The magnetosphere of Jupiter is the cavity created in the
solar wind
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
by
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
's
magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of
Saturn
Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
in the opposite direction, Jupiter's
magnetosphere
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
is the largest and most powerful of any planetary magnetosphere in the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
, and by volume the largest known continuous structure in the Solar System after the
heliosphere
The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding ...
. Wider and flatter than the
Earth's magnetosphere
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
, Jupiter's is stronger by an
order of magnitude
In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are ...
, while its
magnetic moment
In electromagnetism, the magnetic moment or magnetic dipole moment is the combination of strength and orientation of a magnet or other object or system that exerts a magnetic field. The magnetic dipole moment of an object determines the magnitude ...
is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the
Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...
spacecraft in 1973.
Jupiter's internal magnetic field is generated by electrical currents in the planet's outer core, which is theorized to be composed of liquid
metallic hydrogen
Metallic hydrogen is a phase of hydrogen in which it behaves like an electrical conductor. This phase was predicted in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington.
At high pressure and temperatures, metallic hydr ...
. Volcanic eruptions on Jupiter's moon
Io eject large amounts of
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
gas into space, forming a large
torus
In geometry, a torus (: tori or toruses) is a surface of revolution generated by revolving a circle in three-dimensional space one full revolution about an axis that is coplanarity, coplanar with the circle. The main types of toruses inclu ...
around the planet. Jupiter's magnetic field forces the torus to rotate with the same
angular velocity
In physics, angular velocity (symbol or \vec, the lowercase Greek letter omega), also known as the angular frequency vector,(UP1) is a pseudovector representation of how the angular position or orientation of an object changes with time, i ...
and direction as the planet. The torus in turn loads the magnetic field with
plasma, in the process stretching it into a pancake-like structure called a magnetodisk. In effect, Jupiter's magnetosphere is internally driven, shaped primarily by Io's plasma and its own rotation, rather than by the
solar wind
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
as at Earth's magnetosphere.
[ Strong currents in the magnetosphere generate permanent ]aurorae
An aurora ( aurorae or auroras),
also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly observed in high-latitude regions (around the Arc ...
around the planet's poles and intense variable radio emissions, which means that Jupiter can be thought of as a very weak radio pulsar
A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointin ...
. Jupiter's aurorae have been observed in almost all parts of the electromagnetic spectrum
The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...
, including infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
, visible, ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
and soft X-rays
An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
.
The action of the magnetosphere traps and accelerates particles, producing intense belts of radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:
* ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...
similar to Earth's Van Allen belts
The Van Allen radiation belt is a zone of energy, energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetosphere. Earth has two such belts, and sometimes ot ...
, but thousands of times stronger. The interaction of energetic particles with the surfaces of Jupiter's largest moons
A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, a deriva ...
markedly affects their chemical and physical properties. Those same particles also affect and are affected by the motions of the particles within Jupiter's tenuous planetary ring system. Radiation belts present a significant hazard for spacecraft and potentially to human space travellers.
Structure
Jupiter's magnetosphere is a complex structure comprising a bow shock
In astrophysics, bow shocks are shock waves in regions where the conditions of density and pressure change dramatically due to blowing stellar wind. Bow shock occurs when the magnetosphere of an astrophysical object interacts with the nearby fl ...
, magnetosheath
The magnetosheath is the region of space between the magnetopause and the bow shock of a planet's magnetosphere. The regularly organized magnetic field generated by the planet becomes weak and irregular in the magnetosheath due to interaction wit ...
, magnetopause
The magnetopause is the abrupt boundary between a magnetosphere and the surrounding Plasma (physics), plasma. For planetary science, the magnetopause is the boundary between the planet's magnetic field and the solar wind. The location of the ma ...
, magnetotail
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynamo. ...
, magnetodisk, and other components. The magnetic field around Jupiter emanates from a number of different sources, including fluid circulation at the planet's core (the internal field), electrical currents in the plasma surrounding Jupiter and the currents flowing at the boundary of the planet's magnetosphere. The magnetosphere is embedded within the plasma of the solar wind
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
, which carries the interplanetary magnetic field
The interplanetary magnetic field (IMF), also commonly referred to as the heliospheric magnetic field (HMF), is the component of the solar magnetic field that is dragged out from the solar corona by the solar wind flow to fill the Solar System ...
.[ Khurana, 2004, pp. 12–13]
Internal magnetic field
The bulk of Jupiter's magnetic field, like Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
's, is generated by an internal dynamo
"Dynamo Electric Machine" (end view, partly section, )
A dynamo is an electrical generator that creates direct current using a commutator. Dynamos employed electromagnets for self-starting by using residual magnetic field left in the iron cores ...
supported by the circulation of a conducting fluid in its outer core
Earth's outer core is a fluid layer about thick, composed of mostly iron and nickel that lies above Earth's solid Earth's inner core, inner core and below its Earth's mantle, mantle. The outer core begins approximately beneath Earth's surface ...
. But whereas Earth's core is made of molten iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and nickel
Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
, Jupiter's is composed of metallic hydrogen
Metallic hydrogen is a phase of hydrogen in which it behaves like an electrical conductor. This phase was predicted in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington.
At high pressure and temperatures, metallic hydr ...
.[ As with Earth's, Jupiter's magnetic field is mostly a ]dipole
In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways:
* An electric dipole moment, electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple ...
, with north and south magnetic poles at the ends of a single magnetic axis.[ On Jupiter the north pole of the dipole (where magnetic field lines point radially outward) is located in the planet's northern hemisphere and the south pole of the dipole lies in its southern hemisphere. This is opposite from the Earth.][ Jupiter's field also has ]quadrupole
A quadrupole or quadrapole is one of a sequence of configurations of things like electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure re ...
, octupole
A multipole expansion is a mathematical series representing a function that depends on angles—usually the two angles used in the spherical coordinate system (the polar and azimuthal angles) for three-dimensional Euclidean space, \R^3. Multipole e ...
and higher components, though they are less than one-tenth as strong as the dipole component.[ Khurana, 2004, pp. 3–5]
The dipole is tilted roughly 10° from Jupiter's axis of rotation; the tilt is similar to that of the Earth (11.3°).[ Its equatorial field strength is about 417.0 μT (4.170 G), which corresponds to a dipole ]magnetic moment
In electromagnetism, the magnetic moment or magnetic dipole moment is the combination of strength and orientation of a magnet or other object or system that exerts a magnetic field. The magnetic dipole moment of an object determines the magnitude ...
of about 2.83 T· m3. This makes Jupiter's magnetic field about 20 times stronger than Earth's, and its magnetic moment ~20,000 times larger. Jupiter's magnetic field rotates at the same speed as the region below its atmosphere, with a period of 9 h 55 m. No changes in its strength or structure had been observed since the first measurements were taken by the Pioneer
Pioneer commonly refers to a person who is among the first at something that is new to a community.
A pioneer as a settler is among the first settling at a place that is new to the settler community. A historic example are American pioneers, perso ...
spacecraft in the mid-1970s, until 2019. Analysis of observations from the Juno spacecraft show a small but measurable change from the planet's magnetic field observed during the Pioneer era. In particular, Jupiter has a region of strongly non-dipolar field, known as the "Great Blue Spot", near the equator. This may be roughly analogous to the Earth's South Atlantic Anomaly
The South Atlantic Anomaly (SAA) is an area where Earth's inner Van Allen radiation belt comes closest to Earth's surface, dipping down to an altitude of . This leads to an increased flux of energetic particles in this region and exposes orbitin ...
. This region shows signs of large secular variation
The secular variation of a time series is its long-term, non-periodic variation (see '' Decomposition of time series''). Whether a variation is perceived as secular or not depends on the available timescale: a variation that is secular over a times ...
s.
Size and shape
Jupiter's internal magnetic field prevents the solar wind
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
, a stream of ionized particles emitted by the Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, from interacting directly with its atmosphere, and instead diverts it away from the planet, effectively creating a cavity in the solar wind flow, called a magnetosphere, composed of a plasma different from that of the solar wind.[ Khurana, 2004, pp. 1–3] The Jovian magnetosphere is so large that the Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
and its visible corona
Corona (from the Latin for 'crown') most commonly refers to:
* Stellar corona, the outer atmosphere of the Sun or another star
* Corona (beer), a Mexican beer
* Corona, informal term for the coronavirus or disease responsible for the COVID-19 ...
would fit inside it with room to spare.[ Russel, 1993, pp. 715–717] If one could see it from Earth, it would appear five times larger than the full moon in the sky despite being nearly 1700 times farther away.
As with Earth's magnetosphere, the boundary separating the denser and colder solar wind's plasma from the hotter and less dense one within Jupiter's magnetosphere is called the magnetopause
The magnetopause is the abrupt boundary between a magnetosphere and the surrounding Plasma (physics), plasma. For planetary science, the magnetopause is the boundary between the planet's magnetic field and the solar wind. The location of the ma ...
.[ The distance from the magnetopause to the center of the planet is from 45 to 100 ''R''J (where ''R''J=71,492 km is the radius of Jupiter) at the ]subsolar point
The subsolar point on a planet or a moon is the point at which its Sun is perceived to be directly overhead (at the zenith); that is, where the Sun's rays strike the planet exactly perpendicular to its surface. The subsolar point occurs at the ...
—the unfixed point on the surface at which the Sun would appear directly overhead to an observer.[ The position of the magnetopause depends on the pressure exerted by the solar wind, which in turn depends on ]solar activity
Solar phenomena are natural phenomena which occur within the Stellar atmosphere, atmosphere of the Sun. They take many forms, including solar wind, Solar radio emission, radio wave flux, solar flares, coronal mass ejections, Stellar corona#Coron ...
.[ Russell, 2001, pp. 1015–1016] In front of the magnetopause (at a distance from 80 to 130 ''R''J from the planet's center) lies the bow shock
In astrophysics, bow shocks are shock waves in regions where the conditions of density and pressure change dramatically due to blowing stellar wind. Bow shock occurs when the magnetosphere of an astrophysical object interacts with the nearby fl ...
, a wake-like disturbance in the solar wind caused by its collision with the magnetosphere.Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 15–16[ Russel, 1993, pp. 725–727] The region between the bow shock and magnetopause is called the magnetosheath
The magnetosheath is the region of space between the magnetopause and the bow shock of a planet's magnetosphere. The regularly organized magnetic field generated by the planet becomes weak and irregular in the magnetosheath due to interaction wit ...
.
At the opposite side of the planet, the solar wind stretches Jupiter's magnetic field lines into a long, trailing magnetotail
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynamo. ...
, which sometimes extends well beyond the orbit of Saturn
Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
. The structure of Jupiter's magnetotail is similar to Earth's. It consists of two lobes (blue areas in the figure), with the magnetic field in the southern lobe pointing toward Jupiter, and that in the northern lobe pointing away from it. The lobes are separated by a thin layer of plasma called the tail current sheet
A current sheet is an electric current that is confined to a surface, rather than being spread through a volume of space. Current sheets feature in magnetohydrodynamics (MHD), a model of electrically conductive fluids: if there is an electric cu ...
(orange layer in the middle).[ Khurana, 2004, pp. 17–18]
The shape of Jupiter's magnetosphere described above is sustained by the neutral sheet current (also known as the magnetotail current), which flows with Jupiter's rotation through the tail plasma sheet
In the magnetosphere, the plasma sheet is a sheet-like region of denser (0.3-0.5 ions/cm3 versus 0.01-0.02 in the lobes) hot plasma and lower magnetic field
A magnetic field (sometimes called B-field) is a physical field that describes the m ...
, the tail currents, which flow against Jupiter's rotation at the outer boundary of the magnetotail, and the magnetopause currents (or Chapman–Ferraro currents), which flow against rotation along the dayside magnetopause. These currents create the magnetic field that cancels the internal field outside the magnetosphere. They also interact substantially with the solar wind.[ Kivelson, 2005, pp. 303–313]
Jupiter's magnetosphere is traditionally divided into three parts: the inner, middle and outer magnetosphere. The inner magnetosphere is located at distances closer than 10 ''R''J from the planet. The magnetic field within it remains approximately dipole, because contributions from the currents flowing in the magnetospheric equatorial plasma sheet are small. In the middle (between 10 and 40 ''R''J) and outer (further than 40 ''R''J) magnetospheres, the magnetic field is not a dipole, and is seriously disturbed by its interaction with the plasma sheet (see magnetodisk below).[
]
Role of Io
Although overall the shape of Jupiter's magnetosphere resembles that of the Earth's, closer to the planet its structure is very different.[ Jupiter's volcanically active moon Io is a strong source of plasma in its own right, and loads Jupiter's magnetosphere with as much as 1,000 kg of new material every second.][ Khurana, 2004, pp. 5–7] Strong volcanic eruptions on Io emit huge amounts of sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
, a major part of which is dissociated
Dissociation in chemistry is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into other things such as atoms, ions, or radicals, usually in a reversible manner. For instance, when an acid ...
into atoms and ionized
Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
by electron impacts and, to a lesser extent, solar ultraviolet radiation
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...
, producing ions of sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
and oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
. Further electron impacts produce higher charge state, resulting in a plasma of S+, O+, S2+, O2+ and S3+.Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 3–4 They form the ''Io plasma torus'': a thick and relatively cool ring of plasma encircling Jupiter, located near Io's orbit.[ The plasma temperature within the torus is 10–100 eV (100,000–1,000,000 K), which is much lower than that of the particles in the radiation belts—10 keV (100 million K). The plasma in the torus is forced into co-rotation with Jupiter, meaning both share the same period of rotation.][ The Io torus fundamentally alters the dynamics of the Jovian magnetosphere.]Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 1–3
As a result of several processes—diffusion
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
and interchange instability
The interchange instability, also known as the Kruskal–Schwarzschild instability or flute instability, is a type of plasma instability seen in magnetic fusion energy that is driven by the gradients in the magnetic pressure in areas where the c ...
being the main escape mechanisms—the plasma slowly leaks away from Jupiter.Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 4–7 As the plasma moves further from the planet, the radial currents flowing within it gradually increase its velocity, maintaining co-rotation.[ These radial currents are also the source of the magnetic field's azimuthal component, which as a result bends back against the rotation.][ The ]particle number density
In thermodynamics, the particle number (symbol ) of a thermodynamic system is the number of constituent particles in that system. The particle number is a fundamental thermodynamic property which is conjugate to the chemical potential. Unlike m ...
of the plasma decreases from around 2,000 cm−3 in the Io torus to about 0.2 cm−3 at a distance of 35 ''R''J.[ Khurana, 2004, pp. 10–12] In the middle magnetosphere, at distances greater than 10 ''R''J from Jupiter, co-rotation gradually breaks down and the plasma begins to rotate more slowly than the planet.[ Eventually at the distances greater than roughly 40 ''R''J (in the outer magnetosphere) this plasma is no longer confined by the magnetic field and leaves the magnetosphere through the magnetotail.][ Russell, 2001, pp. 1024–1025] As cold, dense plasma moves outward, it is replaced by hot, low-density plasma, with temperatures of up to 20 keV
In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum. When us ...
(200 million K) or higher) moving in from the outer magnetosphere.[ Some of this plasma, adiabatically heated as it approaches Jupiter,][ Khurana, 2004, pp. 20–21] may form the radiation belts in Jupiter's inner magnetosphere.[
]
Magnetodisk
While Earth's magnetic field is roughly teardrop-shaped, Jupiter's is flatter, more closely resembling a disk, and "wobbles" periodically about its axis.[ The main reasons for this disk-like configuration are the ]centrifugal force
Centrifugal force is a fictitious force in Newtonian mechanics (also called an "inertial" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It appears to be directed radially away from the axi ...
from the co-rotating plasma and thermal pressure of hot plasma, both of which act to stretch Jupiter's magnetic field line
A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
s, forming a flattened pancake-like structure, known as the magnetodisk, at the distances greater than 20 ''R''J from the planet.[ Russell, 2001, pp. 1021–1024] The magnetodisk has a thin current sheet at the middle plane,[ approximately near the ]magnetic equator
Magnetic dip, dip angle, or magnetic inclination is the angle made with the horizontal by Earth's magnetic field, Earth's magnetic field lines. This angle varies at different points on Earth's surface. Positive values of inclination indicate t ...
. The magnetic field lines point away from Jupiter above the sheet and towards Jupiter below it.[ The load of plasma from Io greatly expands the size of the Jovian magnetosphere, because the magnetodisk creates an additional internal pressure which balances the pressure of the solar wind.][ In the absence of Io the distance from the planet to the magnetopause at the subsolar point would be no more than 42 ''R''J, whereas it is actually 75 ''R''J on average.][
The configuration of the magnetodisk's field is maintained by the azimuthal ]ring current
A ring current is an electric current carried by charged particles trapped in a planet's magnetosphere. It is caused by the longitudinal drift of energetic (10–200 k eV) particles.
Earth
Earth's ring current is responsible for shielding th ...
(not an analog of Earth's ring current), which flows with rotation through the equatorial plasma sheet.[ Kivelson, 2005, pp. 315–316] The Lorentz force
In electromagnetism, the Lorentz force is the force exerted on a charged particle by electric and magnetic fields. It determines how charged particles move in electromagnetic environments and underlies many physical phenomena, from the operation ...
resulting from the interaction of this current with the planetary magnetic field creates a centripetal force
Centripetal force (from Latin ''centrum'', "center" and ''petere'', "to seek") is the force that makes a body follow a curved trajectory, path. The direction of the centripetal force is always orthogonality, orthogonal to the motion of the bod ...
, which keeps the co-rotating plasma from escaping the planet. The total ring current in the equatorial current sheet is estimated at 90–160 million ampere
The ampere ( , ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to 1 c ...
s.[ Khurana, 2004, pp. 13–16]
Dynamics
Co-rotation and radial currents
The main driver of Jupiter's magnetosphere is the planet's rotation.[ Blanc, 2005, pp. 250–253] In this respect Jupiter is similar to a device called a Unipolar generator
A homopolar generator is a DC electrical generator comprising an electrically conductive disc or cylinder rotating in a plane perpendicular to a uniform static magnetic field. A potential difference is created between the center of the disc and ...
. When Jupiter rotates, its ionosphere moves relatively to the dipole magnetic field of the planet. Because the dipole magnetic moment points in the direction of the rotation,[ the ]Lorentz force
In electromagnetism, the Lorentz force is the force exerted on a charged particle by electric and magnetic fields. It determines how charged particles move in electromagnetic environments and underlies many physical phenomena, from the operation ...
, which appears as a result of this motion, drives negatively charged electrons to the poles, while positively charged ions are pushed towards the equator.[ Cowley, 2001, pp. 1069–76] As a result, the poles become negatively charged and the regions closer to the equator become positively charged. Since the magnetosphere of Jupiter is filled with highly conductive plasma, the electrical circuit
An electrical network is an interconnection of electrical components (e.g., battery (electricity), batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e. ...
is closed through it.[ A current called the direct current flows along the magnetic field lines from the ionosphere to the equatorial plasma sheet. This current then flows radially away from the planet within the equatorial plasma sheet and finally returns to the planetary ionosphere from the outer reaches of the magnetosphere along the field lines connected to the poles. The currents that flow along the magnetic field lines are generally called field-aligned or ]Birkeland current
A Birkeland current (also known as field-aligned current, FAC) is a set of electrical currents that flow along geomagnetic field lines connecting the Earth's magnetosphere to the Earth's high latitude ionosphere. In the Earth's magnetosphere, th ...
s.[ The radial current interacts with the planetary magnetic field, and the resulting Lorentz force accelerates the magnetospheric plasma in the direction of planetary rotation. This is the main mechanism that maintains co-rotation of the plasma in Jupiter's magnetosphere.][
The current flowing from the ionosphere to the plasma sheet is especially strong when the corresponding part of the plasma sheet rotates slower than the planet.] As mentioned above, co-rotation breaks down in the region located between 20 and 40 ''R''J from Jupiter. This region corresponds to the magnetodisk, where the magnetic field is highly stretched.[ Blanc, 2005, pp. 254–261] The strong direct current flowing into the magnetodisk originates in a very limited latitudinal range of about ° from the Jovian magnetic poles. These narrow circular regions correspond to Jupiter's main auroral ovals. (See below.)[ Cowley, 2001, pp. 1083–87] The return current flowing from the outer magnetosphere beyond 50 ''R''J enters the Jovian ionosphere near the poles, closing the electrical circuit. The total radial current in the Jovian magnetosphere is estimated at 60 million–140 million amperes.[
The acceleration of the plasma into the co-rotation leads to the transfer of energy from the Jovian rotation to the ]kinetic energy
In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion.
In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...
of the plasma.[ In that sense, the Jovian magnetosphere is powered by the planet's rotation, whereas the Earth's magnetosphere is powered mainly by the solar wind.][
]
Interchange instability and reconnection
The main problem encountered in deciphering the dynamics of the Jovian magnetosphere is the transport of heavy cold plasma from the Io torus at 6 ''R''J to the outer magnetosphere at distances of more than 50 ''R''J.[ The precise mechanism of this process is not known, but it is hypothesized to occur as a result of plasma diffusion due to interchange instability. The process is similar to the Rayleigh-Taylor instability in ]hydrodynamics
In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in ...
.[ In the case of the Jovian magnetosphere, ]centrifugal force
Centrifugal force is a fictitious force in Newtonian mechanics (also called an "inertial" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It appears to be directed radially away from the axi ...
plays the role of gravity; the heavy liquid is the cold and dense Ionian (i.e. pertaining to Io) plasma, and the light liquid is the hot, much less dense plasma from the outer magnetosphere.[ The instability leads to an exchange between the outer and inner parts of the magnetosphere of ]flux tube
A flux tube is a generally tube-like (cylindrical) region of space containing a magnetic field, B, such that the cylindrical sides of the tube are everywhere parallel to the magnetic field lines. It is a graphical visual aid for visualizing a magn ...
s filled with plasma. The buoyant empty flux tubes move towards the planet, while pushing the heavy tubes, filled with the Ionian plasma, away from Jupiter.[ This interchange of flux tubes is a form of magnetospheric ]turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...
.[ Russell, 2008]
This highly hypothetical picture of the flux tube exchange was partly confirmed by the Galileo spacecraft
''Galileo'' was an American robotic space probe that studied the planet Jupiter and its moons, as well as the asteroids Gaspra and Ida. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It wa ...
, which detected regions of sharply reduced plasma density and increased field strength in the inner magnetosphere.[ These voids may correspond to the almost empty flux tubes arriving from the outer magnetosphere. In the middle magnetosphere, Galileo detected so-called injection events, which occur when hot plasma from the outer magnetosphere impacts the magnetodisk, leading to increased flux of energetic particles and a strengthened magnetic field.]Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 7–9 No mechanism is yet known to explain the transport of cold plasma outward.
When flux tubes loaded with the cold Ionian plasma reach the outer magnetosphere, they go through a reconnection
Magnetic reconnection is a physical process occurring in electrically conducting Plasma (physics), plasmas, in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle accelerati ...
process, which separates the magnetic field from the plasma.[ The former returns to the inner magnetosphere in the form of flux tubes filled with hot and less dense plasma, while the latter are probably ejected down the magnetotail in the form of ]plasmoid
A plasmoid is a coherent structure of Plasma (physics), plasma and magnetic fields. Plasmoids have been proposed to explain natural phenomena such as ball lightning, magnetic bubbles in the magnetosphere, and objects in cometary tails, in the so ...
s—large blobs of plasma. The reconnection processes may correspond to the global reconfiguration events also observed by the Galileo spacecraft, which occurred regularly every 2–3 days.[ The reconfiguration events usually included rapid and chaotic variation of the magnetic field strength and direction, as well as abrupt changes in the motion of the plasma, which often stopped co-rotating and began flowing outward. They were mainly observed in the dawn sector of the night magnetosphere.]Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 11–14 The plasma flowing down the tail along the open field lines is called the planetary wind.[ Khurana, 2004, pp. 18–19]
The reconnection events are analogues to the magnetic substorms in the Earth's magnetosphere.[ The difference seems to be their respective energy sources: terrestrial substorms involve storage of the solar wind's energy in the magnetotail followed by its release through a reconnection event in the tail's neutral current sheet. The latter also creates a plasmoid which moves down the tail.][ Russell, 2001, p. 1011] Conversely, in Jupiter's magnetosphere the rotational energy is stored in the magnetodisk and released when a plasmoid separates from it.[
]
Influence of the solar wind
Whereas the dynamics of the Jovian magnetosphere mainly depend on internal sources of energy, the solar wind probably has a role as well,[ Nichols, 2006, pp. 393–394] particularly as a source of high-energy proton
A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...
s.[ The structure of the outer magnetosphere shows some features of a solar wind-driven magnetosphere, including a significant dawn–dusk asymmetry.][ In particular, magnetic field lines in the dusk sector are bent in the opposite direction to those in the dawn sector.][ In addition, the dawn magnetosphere contains open field lines connecting to the magnetotail, whereas in the dusk magnetosphere, the field lines are closed.][ All these observations indicate that a solar wind driven reconnection process, known on Earth as the ]Dungey cycle
The Dungey cycle, officially proposed by James Dungey in 1961, is a phenomenon that explains interactions between a planet's magnetosphere and solar wind. Dungey originally proposed a cyclic behavior of magnetic reconnection between Earth's magnet ...
, may also be taking place in the Jovian magnetosphere.[
The extent of the solar wind's influence on the dynamics of Jupiter's magnetosphere is currently unknown;]Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 18–19 however, it could be especially strong at times of elevated solar activity.[ Nichols, 2006, pp. 404–405] The auroral radio,[ optical and X-ray emissions,][ as well as ]synchrotron
A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The strength of the magnetic field which bends the particle beam i ...
emissions from the radiation belts all show correlations with solar wind pressure, indicating that the solar wind may drive plasma circulation or modulate internal processes in the magnetosphere.[
]
Emissions
Aurorae
Jupiter demonstrates bright, persistent aurorae around both poles. Unlike Earth's aurorae, which are transient and only occur at times of heightened solar activity, Jupiter's aurorae are permanent, though their intensity varies from day to day. They consist of three main components: the main ovals, which are bright, narrow (less than 1000 km in width) circular features located at approximately 16° from the magnetic poles;[ the satellites' auroral spots, which correspond to the footprints of the magnetic field lines connecting Jupiter's ionosphere with those of its largest moons, and transient polar emissions situated within the main ovals (elliptical field may prove to be a better description).][ Palier, 2001, pp. 1171–73][ Bhardwaj, 2000, pp. 311–316] Auroral emissions have been detected in almost all parts of the electromagnetic spectrum from radio waves to X-rays (up to 3 keV); they are most frequently observed in the mid-infrared (wavelength 3–4 μm and 7–14 μm) and far ultraviolet spectral regions (wavelength 120–180 nm).[ Bhardwaj, 2000, p. 342]
The main ovals are the dominant part of the Jovian aurorae. They have roughly stable shapes and locations,[ but their intensities are strongly modulated by the solar wind pressure—the stronger solar wind, the weaker the aurorae.][ Cowley, 2003, pp. 49–53] As mentioned above, the main ovals are maintained by the strong influx of electrons accelerated by the electric potential drops between the magnetodisk plasma and the Jovian ionosphere.[ Bhardwaj, 2000, pp. 316–319] These electrons carry field aligned currents, which maintain the plasma's co-rotation in the magnetodisk.[ The potential drops develop because the sparse plasma outside the equatorial sheet can only carry a current of a limited strength without driving instabilities and producing potential drops.][ The precipitating electrons have energy in the range 10–100 keV and penetrate deep into the atmosphere of Jupiter, where they ionize and excite molecular hydrogen causing ultraviolet emission.][ Bhardwaj, 2000, pp. 306–311] The total energy input into the ionosphere is 10–100 TW.[ Bhardwaj, 2000, p. 296] In addition, the currents flowing in the ionosphere heat it by the process known as Joule heating
Joule heating (also known as resistive heating, resistance heating, or Ohmic heating) is the process by which the passage of an electric current through a conductor (material), conductor produces heat.
Joule's first law (also just Joule's law), ...
. This heating, which produces up to 300 TW of power, is responsible for the strong infrared radiation from the Jovian aurorae and partially for the heating of the thermosphere of Jupiter.
Spots were found to correspond to the Galilean moons Io, Europa
Europa may refer to:
Places
* Europa (Roman province), a province within the Diocese of Thrace
* Europa (Seville Metro), Seville, Spain; a station on the Seville Metro
* Europa City, Paris, France; a planned development
* Europa Cliffs, Alexan ...
and Ganymede.Clarke
Clarke is a surname which means "clerk". The surname is of English and Irish origin and comes from the Latin . Variants include Clerk and Clark. Clarke is also uncommonly chosen as a given name.
Irish surname origin
Clarke is a common surname ...
, 2002 They develop because the co-rotation of the plasma interacts with the moons and is slowed in their vicinity. The brightest spot belongs to Io, which is the main source of the plasma in the magnetosphere (see above). The Ionian auroral spot is thought to be related to Alfvén currents flowing from the Jovian to Ionian ionosphere. Europa's is similar but much dimmer, because it has a more tenuous atmosphere and is a weaker plasma source. Europa's atmosphere is produced by sublimation of water ice from its surfaces, rather than the volcanic activity which produces Io's atmosphere.[ Blanc, 2005, pp. 277–283] Ganymede has an internal magnetic field and a magnetosphere
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
of its own. The interaction between this magnetosphere and that of Jupiter produces currents due to magnetic reconnection
Magnetic reconnection is a physical process occurring in electrically conducting Plasma (physics), plasmas, in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle accelerati ...
. The auroral spot associated with Callisto is probably similar to that of Europa, but has only been seen once as of June, 2019. Normally, magnetic field lines connected to Callisto touch Jupiter's atmosphere very close to or along the main auroral oval, making it difficult to detect Callisto's auroral spot.
Bright arcs and spots sporadically appear within the main ovals. These transient phenomena are thought to be related to interaction with either the solar wind or the dynamics of the outer magnetosphere.[ The magnetic field lines in this region are believed to be open or to map onto the magnetotail.][ The secondary ovals are sometimes observed inside the main oval and may be related to the boundary between open and closed magnetic field lines or to the polar ]cusp
A cusp is the most pointed end of a curve. It often refers to cusp (anatomy), a pointed structure on a tooth.
Cusp or CUSP may also refer to:
Mathematics
* Cusp (singularity), a singular point of a curve
* Cusp catastrophe, a branch of bifu ...
s.[ Palier, 2001, pp. 1170–71] The polar auroral emissions could be similar to those observed around Earth's poles: appearing when electrons are accelerated towards the planet by potential drops, during reconnection of solar magnetic field with that of the planet.[ The regions within the main ovals emits most of auroral X-rays. The spectrum of the auroral X-ray radiation consists of ]spectral line
A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission (electromagnetic radiation), emission or absorption (electromagnetic radiation), absorption of light in a narrow frequency ...
s of highly ionized oxygen and sulfur, which probably appear when energetic (hundreds of kiloelectronvolts) S and O ions precipitate into the polar atmosphere of Jupiter. The source of this precipitation remains unknown but this is inconsistent with the theory that these magnetic field lines are open and connect to the solar wind.[ Elsner, 2005, pp. 419–420]
Jupiter at radio wavelengths
Jupiter is a powerful source of radio wave
Radio waves (formerly called Hertzian waves) are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths g ...
s in the spectral regions stretching from several kilohertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base ...
to tens of megahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base ...
. Radio waves with frequencies
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
of less than about 0.3 MHz (and thus wavelengths longer than 1 km) are called the Jovian kilometric radiation or KOM. Those with frequencies in the interval of 0.3–3 MHz (with wavelengths of 100–1000 m) are called the hectometric radiation or HOM, while emissions in the range 3–40 MHz (with wavelengths of 10–100 m) are referred to as the decametric radiation or DAM. The latter radiation was the first to be observed from Earth, and its approximately 10-hour periodicity helped to identify it as originating from Jupiter. The strongest part of decametric emission, which is related to Io and to the Io–Jupiter current system, is called Io-DAM.Zarka
Zarqa () is the capital of Zarqa Governorate in Jordan. Its name means "the blue (city)". It had a population of 635,160 inhabitants in 2015, and is the second most populous city in Jordan after Amman.
History
Although the area has been inhab ...
, 1998, pp. 20,160–168
The majority of these emissions are thought to be produced by a mechanism called "cyclotron maser instability", which develops close to the auroral regions. Electrons moving parallel to the magnetic field precipitate into the atmosphere while those with a sufficient perpendicular velocity are reflected by the converging magnetic field. This results in an unstable velocity distribution. This velocity distribution spontaneously generates radio waves at the local electron cyclotron frequency. The electrons involved in the generation of radio waves are probably those carrying currents from the poles of the planet to the magnetodisk.Zarka
Zarqa () is the capital of Zarqa Governorate in Jordan. Its name means "the blue (city)". It had a population of 635,160 inhabitants in 2015, and is the second most populous city in Jordan after Amman.
History
Although the area has been inhab ...
, 1998, pp. 20, 173–181 The intensity of Jovian radio emissions usually varies smoothly with time. However, there are short and powerful bursts (S bursts) of emission superimposed on the more gradual variations and which can outshine all other components. The total emitted power of the DAM component is about 100 GW, while the power of all other HOM/KOM components is about 10 GW. In comparison, the total power of Earth's radio emissions is about 0.1 GW.[
Jupiter's radio and particle emissions are strongly modulated by its rotation, which makes the planet somewhat similar to a ]pulsar
A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its Poles of astronomical bodies#Magnetic poles, magnetic poles. This radiation can be obse ...
.Hill
A hill is a landform that extends above the surrounding terrain. It often has a distinct summit, and is usually applied to peaks which are above elevation compared to the relative landmass, though not as prominent as Mountain, mountains. Hills ...
, 1995 This periodical modulation is probably related to asymmetries in the Jovian magnetosphere, which are caused by the tilt of the magnetic moment with respect to the rotational axis as well as by high-latitude magnetic anomalies. The physics governing Jupiter's radio emissions is similar to that of radio pulsars. They differ only in the scale, and Jupiter can be considered a very small radio pulsar
A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointin ...
too.[ In addition, Jupiter's radio emissions strongly depend on solar wind pressure and, hence, on ]solar activity
Solar phenomena are natural phenomena which occur within the Stellar atmosphere, atmosphere of the Sun. They take many forms, including solar wind, Solar radio emission, radio wave flux, solar flares, coronal mass ejections, Stellar corona#Coron ...
.[
In addition to relatively long-wavelength radiation, Jupiter also emits ]synchrotron radiation
Synchrotron radiation (also known as magnetobremsstrahlung) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in some types ...
(also known as the Jovian decimetric radiation or DIM radiation) with frequencies in the range of 0.1–15 GHz (wavelength from 3 m to 2 cm),.[ These emissions are from relativistic electrons trapped in the inner radiation belts of the planet. The energy of the electrons that contribute to the DIM emissions is from 0.1 to 100 MeV,][ Santos-Costa, 2001] while the leading contribution comes from the electrons with energy in the range 1–20 MeV.Bolton
Bolton ( , locally ) is a town in Greater Manchester in England. In the foothills of the West Pennine Moors, Bolton is between Manchester, Blackburn, Wigan, Bury, Greater Manchester, Bury and Salford. It is surrounded by several towns and vill ...
, 2002 This radiation is well understood and was used since the beginning of the 1960s to study the structure of the planet's magnetic field and radiation belts.Zarka
Zarqa () is the capital of Zarqa Governorate in Jordan. Its name means "the blue (city)". It had a population of 635,160 inhabitants in 2015, and is the second most populous city in Jordan after Amman.
History
Although the area has been inhab ...
, 2005, pp. 384–385 The particles in the radiation belts originate in the outer magnetosphere and are adiabatically accelerated, when they are transported to the inner magnetosphere.[ However, this requires a source population of moderately high energy electrons (>> 1 keV), and the origin of this population is not well understood.
Jupiter's magnetosphere ejects streams of high-energy electrons and ions (energy up to tens ]megaelectronvolt
In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum. When ...
s), which travel as far as Earth's orbit.Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2004, pp. 17–18 These streams are highly collimated
A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates. A laser beam is an archetypical example. A perfectly collimated light beam, with no divergence, would not disp ...
and vary with the rotational period of the planet like the radio emissions. In this respect as well, Jupiter shows similarity to a pulsar.[
]
Interaction with rings and moons
Jupiter's extensive magnetosphere envelops its ring system and the orbits of all four Galilean satellites
The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter. They are, in descending-size order, Ganymede, Callisto, Io, and Europa. They are the most readily visible Solar System objects after Saturn, the dimmest of ...
.[ Orbiting near the magnetic equator, these bodies serve as sources and sinks of magnetospheric plasma, while energetic particles from the magnetosphere alter their surfaces. The particles ]sputter
In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and c ...
off material from the surfaces and create chemical changes via radiolysis
Radiolysis is the dissociation of molecules by ionizing radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux. The radiation in this context is associated with ionizing radiation; radiolysis is ...
.Johnson
Johnson may refer to:
People and fictional characters
*Johnson (surname), a common surname in English
* Johnson (given name), a list of people
* List of people with surname Johnson, including fictional characters
*Johnson (composer) (1953–2011) ...
, 2004, pp. 1–2 The plasma's co-rotation with the planet means that the plasma preferably interacts with the moons' trailing hemispheres, causing noticeable hemispheric asymmetries.Johnson
Johnson may refer to:
People and fictional characters
*Johnson (surname), a common surname in English
* Johnson (given name), a list of people
* List of people with surname Johnson, including fictional characters
*Johnson (composer) (1953–2011) ...
, 2004, pp. 3–5
Close to Jupiter, the planet's rings and small moons absorb high-energy particles (energy above 10 keV) from the radiation belts.[ This creates noticeable gaps in the belts' spatial distribution and affects the decimetric synchrotron radiation. In fact, the existence of Jupiter's rings was first hypothesized on the basis of data from the ]Pioneer 11
''Pioneer 11'' (also known as ''Pioneer G'') is a NASA robotic space probe launched on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, the solar wind, and cosmic rays. It was the first probe to Exploration ...
spacecraft, which detected a sharp drop in the number of high-energy ions close to the planet.Burns
Burns may refer to:
Astronomy
* 2708 Burns, an asteroid
* Burns (crater), on Mercury
People
* Burns (surname), list of people and characters named Burns
** Burns (musician), Scottish record producer
Places in the United States
* Burns, ...
, 2004, pp. 1–2 The planetary magnetic field strongly influences the motion of sub-micrometer ring particles as well, which acquire an electrical charge under the influence of solar ultraviolet radiation
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...
. Their behavior is similar to that of co-rotating ion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s.Burns
Burns may refer to:
Astronomy
* 2708 Burns, an asteroid
* Burns (crater), on Mercury
People
* Burns (surname), list of people and characters named Burns
** Burns (musician), Scottish record producer
Places in the United States
* Burns, ...
, 2004, pp. 12–14 Resonant interactions between the co-rotation and the particles' orbital motion has been used to explain the creation of Jupiter's innermost halo ring (located between 1.4 and 1.71 ''R''J). This ring consists of sub-micrometer particles on highly inclined and eccentric orbits.Burns
Burns may refer to:
Astronomy
* 2708 Burns, an asteroid
* Burns (crater), on Mercury
People
* Burns (surname), list of people and characters named Burns
** Burns (musician), Scottish record producer
Places in the United States
* Burns, ...
, 2004, pp. 10–11 The particles originate in the main ring; however, when they drift toward Jupiter, their orbits are modified by the strong 3:2 Lorentz resonance located at 1.71 ''R''J, which increases their inclinations and eccentricities. Another 2:1 Lorentz resonance at 1.4 Rj defines the inner boundary of the halo ring.Burns
Burns may refer to:
Astronomy
* 2708 Burns, an asteroid
* Burns (crater), on Mercury
People
* Burns (surname), list of people and characters named Burns
** Burns (musician), Scottish record producer
Places in the United States
* Burns, ...
, 2004, pp. 17–19
All Galilean moons have thin atmospheres with surface pressures in the range 0.01–1 nbar, which in turn support substantial ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...
s with electron densities in the range of 1,000–10,000 cm−3.[ Kivelson, 2004, pp. 2–4] The co-rotational flow of cold magnetospheric plasma is partially diverted around them by the currents induced in their ionospheres, creating wedge-shaped structures known as Alfvén wings.[ Kivelson, 2004, pp. 8–10] The interaction of the large moons with the co-rotational flow is similar to the interaction of the solar wind
The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
with the non-magnetized planets like Venus
Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
, although the co-rotational speed is usually subsonic (the speeds vary from 74 to 328 km/s), which prevents the formation of a bow shock
In astrophysics, bow shocks are shock waves in regions where the conditions of density and pressure change dramatically due to blowing stellar wind. Bow shock occurs when the magnetosphere of an astrophysical object interacts with the nearby fl ...
.[ Kivelson, 2004, pp. 1–2] The pressure from the co-rotating plasma continuously strips gases from the moons' atmospheres (especially from that of Io), and some of these atoms are ionized and brought into co-rotation. This process creates gas and plasma tori in the vicinity of moons' orbits with the Ionian torus being the most prominent. In effect, the Galilean moons (mainly Io) serve as the principal plasma sources in Jupiter's inner and middle magnetosphere. Meanwhile, the energetic particles are largely unaffected by the Alfvén wings and have free access to the moons' surfaces (except Ganymede's).[ Cooper, 2001, pp. 137,139]
The icy Galilean moons, Europa
Europa may refer to:
Places
* Europa (Roman province), a province within the Diocese of Thrace
* Europa (Seville Metro), Seville, Spain; a station on the Seville Metro
* Europa City, Paris, France; a planned development
* Europa Cliffs, Alexan ...
, Ganymede and Callisto
CALLISTO (''Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations'') is a reusable VTVL Prototype, demonstrator propelled by a small 40 kN Japanese LOX-LH2 rocket engine. It is being developed jointly by the CNES, French ...
, all generate induced magnetic moments in response to changes in Jupiter's magnetic field. These varying magnetic moments create dipole magnetic fields around them, which act to compensate for changes in the ambient field.[ The induction is thought to take place in subsurface layers of salty water, which are likely to exist in all of Jupiter's large icy moons. These underground oceans can potentially harbor life, and evidence for their presence was one of the most important discoveries made in the 1990s by ]spacecraft
A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...
.[ Kivelson, 2004, pp. 10–11]
The interaction of the Jovian magnetosphere with Ganymede, which has an intrinsic magnetic moment, differs from its interaction with the non-magnetized moons.[ Ganymede's internal magnetic field carves a cavity inside Jupiter's magnetosphere with a diameter of approximately two Ganymede diameters, creating a mini-magnetosphere within Jupiter's magnetosphere. Ganymede's magnetic field diverts the co-rotating plasma flow around its magnetosphere. It also protects the moon's equatorial regions, where the field lines are closed, from energetic particles. The latter can still freely strike Ganymede's poles, where the field lines are open.][ Kivelson, 2004, pp. 16–18] Some of the energetic particles are trapped near the equator of Ganymede, creating mini-radiation belts.[ Williams, 1998, p. 1] Energetic electrons entering its thin atmosphere are responsible for the observed Ganymedian polar aurorae.[
Charged particles have a considerable influence on the surface properties of Galilean moons. Plasma originating from Io carries sulfur and ]sodium
Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
ions farther from the planet,[ Cooper, 2001, pp. 154–156] where they are implanted preferentially on the trailing hemispheres of Europa and Ganymede.Johnson
Johnson may refer to:
People and fictional characters
*Johnson (surname), a common surname in English
* Johnson (given name), a list of people
* List of people with surname Johnson, including fictional characters
*Johnson (composer) (1953–2011) ...
, 2004, pp. 15–19 On Callisto however, for unknown reasons, sulfur is concentrated on the leading hemisphere.[ Hibbitts, 2000, p. 1] Plasma may also be responsible for darkening the moons' trailing hemispheres (again, except Callisto's).[ Energetic electrons and ions, with the flux of the latter being more isotropic, bombard surface ice, sputtering atoms and molecules off and causing ]radiolysis
Radiolysis is the dissociation of molecules by ionizing radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux. The radiation in this context is associated with ionizing radiation; radiolysis is ...
of water and other chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
s. The energetic particles break water into oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
and hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
, maintaining the thin oxygen atmospheres of the icy moons (since the hydrogen escapes more rapidly). The compounds produced radiolytically on the surfaces of Galilean moons also include ozone
Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...
and hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
.[ If organics or ]carbonate
A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...
s are present, carbon dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
, methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
and carbonic acid
Carbonic acid is a chemical compound with the chemical formula . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion ...
can be produced as well. In the presence of sulfur, likely products include sulfur dioxide, hydrogen disulfide
Hydrogen disulfide is the inorganic compound with the formula . This hydrogen chalcogenide is a pale yellow volatile liquid with a camphor-like odor. It decomposes readily to hydrogen sulfide () and elemental sulfur.
Structure
The connection of ...
and sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
.Johnson
Johnson may refer to:
People and fictional characters
*Johnson (surname), a common surname in English
* Johnson (given name), a list of people
* List of people with surname Johnson, including fictional characters
*Johnson (composer) (1953–2011) ...
, 2004, pp. 8–13 Oxidant
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "Electron acceptor, accepts"/"receives" an electron from a (called the , , or ''electr ...
s produced by radiolysis, like oxygen and ozone, may be trapped inside the ice and carried downward to the oceans over geologic time intervals, thus serving as a possible energy source for life.
Discovery
The first evidence for the existence of Jupiter's magnetic field came in 1955, with the discovery of the decametric radio emission or DAM.[ Burke and Franklin, 1955] As the DAM's spectrum extended up to 40 MHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...
, astronomers concluded that Jupiter must possess a magnetic field with a maximum strength of above 1 milli teslas (10 gauss
Johann Carl Friedrich Gauss (; ; ; 30 April 177723 February 1855) was a German mathematician, astronomer, Geodesy, geodesist, and physicist, who contributed to many fields in mathematics and science. He was director of the Göttingen Observat ...
).Zarka
Zarqa () is the capital of Zarqa Governorate in Jordan. Its name means "the blue (city)". It had a population of 635,160 inhabitants in 2015, and is the second most populous city in Jordan after Amman.
History
Although the area has been inhab ...
, 2005, pp. 371–375
In 1959, observations in the microwave
Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
part of the electromagnetic (EM) spectrum (0.1–10 GHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...
) led to the discovery of the Jovian decimetric radiation (DIM) and the realization that it was synchrotron radiation
Synchrotron radiation (also known as magnetobremsstrahlung) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in some types ...
emitted by relativistic electrons trapped in the planet's radiation belts.Drake
Drake may refer to:
Animals and creatures
* A male duck
* Drake (mythology), a term related to and often synonymous with dragon
People and fictional characters
* Drake (surname), a list of people and fictional characters with the family ...
, 1959 These synchrotron emissions were used to estimate the number and energy of the electrons around Jupiter and led to improved estimates of the magnetic moment and its tilt.[
By 1973 the magnetic moment was known within a factor of two, whereas the tilt was correctly estimated at about 10°.][ The modulation of Jupiter's DAM by Io (the so-called Io-DAM) was discovered in 1964, and allowed Jupiter's ]rotation period
In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...
to be precisely determined.Zarka
Zarqa () is the capital of Zarqa Governorate in Jordan. Its name means "the blue (city)". It had a population of 635,160 inhabitants in 2015, and is the second most populous city in Jordan after Amman.
History
Although the area has been inhab ...
, 2005, pp. 375–377 The definitive discovery of the Jovian magnetic field occurred in December 1973, when the Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...
spacecraft flew near the planet.Smith
Smith may refer to:
People and fictional characters
* Metalsmith, or simply smith, a craftsman fashioning tools or works of art out of various metals
* Smith (given name)
* Smith (surname), a family name originating in England
** List of people ...
, 1974
Exploration after 1970
As of 2009 a total of eight spacecraft have flown around Jupiter and all have contributed to the present knowledge of the Jovian magnetosphere. The first space probe to reach Jupiter was Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...
in December 1973, which passed within 2.9 ''R''J[ from the center of the planet.][ Its twin ]Pioneer 11
''Pioneer 11'' (also known as ''Pioneer G'') is a NASA robotic space probe launched on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, the solar wind, and cosmic rays. It was the first probe to Exploration ...
visited Jupiter a year later, traveling along a highly inclined trajectory and approaching the planet as close as 1.6 ''R''J.[
Pioneer 10 provided the best coverage available of the inner magnetic field][ as it passed through the inner radiation belts within 20 ''R''J, receiving an integrated dose of 200,000 rads from ]electrons
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
and 56,000 rads from protons
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' ( elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an electron (the pro ...
(for a human, a whole body dose of 500 rads would be fatal). The level of radiation at Jupiter was ten times more powerful than Pioneer's designers had predicted, leading to fears that the probe would not survive; however, with a few minor glitches, it managed to pass through the radiation belts, saved in large part by the fact that Jupiter's magnetosphere had "wobbled" slightly upward at that point, moving away from the spacecraft. However, Pioneer 11 did lose most images of Io, as the radiation had caused its imaging photo polarimeter
A polarimeter is a scientific instrument used to measure optical rotation: the angle of rotation caused by passing linearly polarized light through an Optical activity, optically active substance.
Some chemical substances are optically active, ...
to receive a number of spurious commands. The subsequent and far more technologically advanced Voyager
Voyager may refer to:
Computing and communications
* LG Voyager, a mobile phone model manufactured by LG Electronics
* NCR Voyager, a computer platform produced by NCR Corporation
* Voyager (computer worm), a computer worm affecting Oracle ...
spacecraft had to be redesigned to cope with the massive radiation levels.Wolverton
Wolverton ( ) is a constituent town of Milton Keynes
Milton Keynes ( ) is a city status in the United Kingdom, city in Buckinghamshire, England, about north-west of London. At the 2021 Census, the population of Milton Keynes urban ar ...
, 2004, pp. 100–157
Voyagers 1 and 2 arrived at Jupiter in 1979–1980 and traveled almost in its equatorial plane. Voyager 1
''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and the interstellar medium, interstellar space beyond the Sun's heliosphere. It was launched 16 days afte ...
, which passed within 5 ''R''J from the planet's center,[ was first to encounter the Io plasma torus.][ It received a radiation dosage one thousand times the lethal level for humans, the damage resulting in serious degradation of some high-resolution images of Io and Ganymede. ]Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program. It was launched on a trajectory towards the gas giants (Jupiter and Saturn) and enabled further encounters with the ice giants (Uranus and ...
passed within 10 ''R''J[ and discovered the current sheet in the equatorial plane. The next probe to approach Jupiter was '' Ulysses'' in 1992, which investigated the planet's polar magnetosphere.][
The ''Galileo'' spacecraft, which orbited Jupiter from 1995 to 2003, provided a comprehensive coverage of Jupiter's magnetic field near the equatorial plane at distances up to 100 ''R''J. The regions studied included the magnetotail and the dawn and dusk sectors of the magnetosphere.][ While Galileo successfully survived in the harsh radiation environment of Jupiter, it still experienced a few technical problems. In particular, the spacecraft's ]gyroscope
A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining Orientation (geometry), orientation and angular velocity. It is a spinning wheel or disc in ...
s often exhibited increased errors. Several times electrical arc
An electric arc (or arc discharge) is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma, which may produce visible light. An a ...
s occurred between rotating and non-rotating parts of the spacecraft, causing it to enter safe mode
Safe mode is a diagnosis, diagnostic mode of a computer operating system (OS). It can also refer to a mode of operation by application software. ''Safe mode'' is intended to help fix most, if not all, problems within an operating system. It is a ...
, which led to total loss of the data from the 16th, 18th and 33rd orbits. The radiation also caused phase shifts in ''Galileos ultra-stable quartz oscillator
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock ...
.Fieseler
The Gerhard Fieseler Werke (GFW) in Kassel was a German aircraft manufacturer of the 1930s and 1940s. The company is remembered mostly for its military aircraft built for the Luftwaffe during the Second World War.
History
Gerhard Fieseler, the ...
, 2002
When the '' Cassini'' spacecraft flew by Jupiter in 2000, it conducted coordinated measurements with ''Galileo''.[ '']New Horizons
''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...
'' passed close to Jupiter in 2007, carrying out a unique investigation of the Jovian magnetotail, traveling as far as 2500 ''R''J along its length.Krupp
Friedrich Krupp AG Hoesch-Krupp (formerly Fried. Krupp AG and Friedrich Krupp GmbH), trade name, trading as Krupp, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer dur ...
, 2007, p. 216 In July 2016 '' Juno'' was inserted into Jupiter orbit, its scientific objectives include exploration of Jupiter's polar magnetosphere. The coverage of Jupiter's magnetosphere remains much poorer than for Earth's magnetic field. Further study is important to further understand the Jovian magnetosphere's dynamics.[
In 2003, ]NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
conducted a conceptual study called "Human Outer Planets Exploration" (HOPE) regarding the future human exploration of the outer Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sol ...
. The possibility was mooted of building a surface base on Callisto, because of the low radiation levels at the moon's distance from Jupiter and its geological stability. Callisto is the only one of Jupiter's Galilean satellites for which human exploration is feasible. The levels of ionizing radiation
Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...
on Io, Europa and Ganymede are inimical to human life, and adequate protective measures have yet to be devised.[ Troutman, 2003]
Exploration after 2010
The ''Juno'' New Frontiers mission to Jupiter was launched in 2011 and arrived at Jupiter in 2016. It includes a suite of instruments designed to better understand the magnetosphere, including a magnetometer
A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
as well as other devices such as a detector for plasma and radio waves called ''Waves''.
The Jovian Auroral Distributions Experiment (JADE) instrument should also help to understand the magnetosphere.
''Juno'' revealed a planetary magnetic field rich in spatial variation, possibly due to a relatively large dynamo radius. The most surprising observation until late 2017 was the absence of the expected magnetic signature of intense field aligned currents ( Birkeland currents) associated with the main aurora.
One of the goals of the European Space Agency's Jupiter Icy Moons Explorer
The Jupiter Icy Moons Explorer (Juice, formerly JUICE) is an interplanetary spacecraft on its way to orbit and study three icy moons of Jupiter (planet), Jupiter: Ganymede (moon), Ganymede, Callisto (moon), Callisto, and Europa (moon), Europa ...
(JUICE) mission, launched April, 2023, is to understand the magnetic field from Ganymede and how it impacts Jupiter. Tianwen-4 is a proposed Chinese mission that will either explore the moon Callisto or gather more information on Io.
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{{DEFAULTSORT:Magnetosphere Of Jupiter
Astronomical objects discovered in 1973
Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
Planetary science