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L-shell
The L-shell, L-value, or McIlwain L-parameter (after Carl E. McIlwain) is a parameter describing a particular set of planetary magnetic field lines. Colloquially, L-value often describes the set of magnetic field lines which cross the Earth's magnetic equator at a number of Earth's radius, Earth-radii equal to the L-value. For example, L = 2 describes the set of the Earth's magnetic field lines which cross the Earth's magnetic equator two earth radii from the center of the Earth. L-shell parameters can also describe the magnetic fields of other planets. In such cases, the parameter is renormalized for that planet's radius and magnetic field model.Galileo - Glossary of Selected Terms'' NASA Jet Propulsion Laboratory, (2003). Although L-value is formally defined in terms of the Earth's true instantaneous magnetic field (or a high-order model like International Geomagnetic Reference Field, IGRF), it is often used to give a general picture of magnetic phenomena near the Earth, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipole Model Of The Earth's Magnetic Field
The dipole model of the Earth's magnetic field is a first order approximation of the rather complex true Earth's magnetic field. Due to effects of the interplanetary magnetic field (IMF), and the solar wind, the magnetic dipole, dipole model is particularly inaccurate at high L-shells (e.g., above L=3), but may be a good approximation for lower L-shells. For more precise work, or for any work at higher L-shells, a more accurate model that incorporates solar effects, such as the Tsyganenko magnetic field model, is recommended. Formulation The following equations describe the dipole magnetic field. First, define B_0 as the mean value of the magnetic field at the magnetic equator on the Earth's surface. Typically B_0=3.12\times10^\ \textrm. Then, the radial and latitudinal fields can be described as :B_r = -2B_0\left(\frac\right)^3\cos\theta :B_\theta = -B_0\left(\frac\right)^3\sin\theta :, B, = B_0\left(\frac\right)^3 \sqrt where R_E is the mean Earth radius, radius of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Van Allen Radiation Belt
The Van Allen radiation belt is a zone of 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 others may be temporarily created. The belts are named after James Van Allen, who published an article describing the belts in 1958. Earth's two main belts extend from an altitude of about above the surface, in which region radiation levels vary. The belts are in the inner region of Earth's magnetic field. They trap energetic electrons and protons. Other nuclei, such as alpha particles, are less prevalent. Most of the particles that form the belts are thought to come from the solar wind while others arrive as cosmic rays. By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction. The belts endanger satellites, which must have their sensitive components protected with adequat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aurora (astronomy)
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 Arctic and Antarctic). Auroras display dynamic patterns of radiant lights that appear as curtains, rays, spirals or dynamic flickers covering the entire sky. Auroras are the result of disturbances in the Earth's magnetosphere caused by enhanced speeds of solar wind from coronal holes and coronal mass ejections. These disturbances alter the trajectories of charged particles in the magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere ( thermosphere/exosphere). The resulting ionization and excitation of atmospheric constituents emit light of varying color and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of accelera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomagnetic Latitude
Geomagnetic latitude, or magnetic latitude (MLAT), is a parameter analogous to geographic latitude, except that, instead of being defined relative to the geographic poles, it is defined by the axis of the geomagnetic dipole, which can be accurately extracted from the International Geomagnetic Reference Field (IGRF). Further, Magnetic Local Time (MLT) is the geomagnetic dipole equivalent to geographic longitude. See also * Earth's magnetic field * Geomagnetic equator * Ionosphere * L-shell * Magnetosphere * World Magnetic Model (WMM) References External links Tips on Viewing the Aurora( SWPC) Magnetic Field Calculator(NCEI The National Centers for Environmental Information (NCEI) is a U.S. government agency that manages one of the world's largest archives of atmospheric, coastal, geophysical, and oceanic data. The current director is Deke Arndt. NCEI is operate ...) Ionospheric Electrodynamics Using Magnetic Apex Coordinates( Journal of Geomagnetism and Geoelectricity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Mirror Point
In astrophysics, a magnetic mirror point is a point where the motion of a electric charge, charged particle trapped in a magnetic field (such as the (approximately) dipole field of the Earth's magnetic field, Earth) reverses its direction. More precisely, it is the point where the projection of the particle's velocity vector (mathematics), vector in the direction of the field vector is equal to zero. Whenever charged particles from the sun hit Earth's magnetosphere, it is observed that the magnetic field of Earth reverses direction. Since the forces that generate our magnetic field are constantly changing, the field itself is also in continual flux, its strength waxing and waning over time. This causes the location of Earth's magnetic north and south poles to gradually shift, and to even completely flip locations every 300,000 years or so. See also * Magnetic mirror * L-shell * Dipole model of the Earth's magnetic field * List of artificial radiation belts References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L Shell Global Dipole
L, or l, is the twelfth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''el'' (pronounced ), plural ''els''. History Lamedh may have come from a pictogram of an ox goad or cattle prod. Some have suggested that it represents a shepherd's staff. Typographic variants In most sans-serif typefaces, the lowercase letter ''ell'' , written as the glyph , may be difficult to distinguish from the uppercase letter "eye" (written as the glyph ); in some serif typefaces, the glyph may be confused with the glyph , the digit ''one''. To avoid such confusion, some newer computer fonts (such as Trebuchet MS) have a finial, a curve to the right at the bottom of the lowercase letter ''ell''. Other style variants are provided in script typefaces and display typefaces. All these variants of the letter are encoded in Unicode as or , allowing presentation to be chosen accor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pitch Angle (particle Motion)
The pitch angle of a charged particle is the angle between the particle's velocity vector and the local magnetic field. This is a common measurement and topic when studying the magnetosphere, magnetic mirrors, biconic cusps and polywells. Usage It is customary to discuss the direction a particle is heading by its pitch angle. A pitch angle of 0 degrees is a particle whose parallel motion is perfectly along the local magnetic field. In the northern hemisphere this particle would be heading down toward the Earth (and the opposite in the southern hemisphere). A pitch angle of 90 degrees is a particle that is locally mirroring. Special case The equatorial pitch angle of a particle is the pitch angle of the particle at the Earth's geomagnetic equator. This angle defines the loss cone of a particle. The loss cone is the set of angles where the particle will strike the atmosphere and no longer be trapped in the magnetosphere while particles with pitch angles outside the loss co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imke De Pater
Imke de Pater is a Dutch astronomer working at the University of California, Berkeley. She is known for her research on the large planets and led the team using the Keck Telescope to image the 1994 impact of the comet Comet Shoemaker–Levy 9 with Jupiter. Education and career De Pater was introduced to astronomy in high school when a family friend gave her an astronomy textbook and introduced her to someone in Utrecht so she could learn about the field. She earned her Ph.D. from Leiden University (1980) while working on radio emissions from Jupiter. de Pater is a professor of astronomy, earth and planetary science from the University of California, Berkeley, and served as the chair of the Astronomy Department. In 2015 de Pater was named a fellow of the American Geophysical Union who cited her for: Research De Pater's research centers on observations of the large planets and their rings and satellites (Jupiter, Neptune, Titan, and Uranus) using adaptive optics and radio obs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 "Solar System" and "solar system" structures in theinaming guidelines document. The name is commonly rendered in lower case ('solar system'), as, for example, in the ''Oxford English Dictionary'' an''Merriam-Webster's 11th Collegiate Dictionary''. is the gravitationally bound Planetary system, system of the Sun and the objects that orbit it. It Formation and evolution of the Solar System, formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is a typical star that maintains a hydrostatic equilibrium, balanced equilibrium by the thermonuclear fusion, fusion of hydrogen into helium at its stellar core, core, releasing this energy from its outer photosphere. As ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetosphere Of Jupiter
The magnetosphere of Jupiter is the cavity created in the solar wind by Jupiter's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment 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 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. Volcanic eruptions on Jupiter's moon Io (moon), Io eject large ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmapause
The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined by an order of magnitude drop in plasma density. In 1963 American scientist Don Carpenter and Soviet astronomer proved the plasmasphere and plasmapause's existence from the analysis of very low frequency (VLF) whistler wave data. Traditionally, the plasmasphere has been regarded as a well behaved cold plasma with particle motion dominated entirely by the geomagnetic field and, hence, co-rotating with the Earth. History The discovery of the plasmasphere grew out of the scientific study of whistlers, natural phenomena caused by very low frequency (VLF) radio waves. Whistlers were first heard by radio operators in the 1890s. British scientist Llewelyn Robert Owen Storey had shown lightning generated whistlers in his 1953 PhD dissertation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomagnetic Storm
A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth's magnetosphere that is driven by interactions between the magnetosphere and large-scale transient Plasma (physics), plasma and magnetic field structures that originate on or near the Sun. The structures that produce geomagnetic storms include interplanetary coronal mass ejections (CME) and corotating interaction regions (CIR). The former often originate from solar active regions, while the latter originate at the boundary between high- and low-speed streams of solar wind. The frequency of geomagnetic storms increases and decreases with the sunspot cycle. During solar maximum, solar maxima, geomagnetic storms occur more often, with the majority driven by CMEs. When these structures reach Earth, the increase in the solar wind pressure initially compresses the magnetosphere. The solar wind's magnetic field interacts with the Earth's magnetic field and transfers an increased energy into th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
