Ionospheric storms are

storm A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstor ...

s which contain varying densities of energised

electron 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 ...

s in the

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 ...

as produced from the Sun. Ionospheric storms are caused by

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 structur ...

s. They are categorised into positive and negative storms, where positive storms have a high density of electrons and negative storms contain a lower density. The

total electron content Total electron content (TEC) is an important descriptive quantity for the ionosphere of the Earth. TEC is the total number of electrons integrated between two points, along a tube of one meter squared cross section, i.e., the electron columnar ...

(TEC) is used to measure these densities, and is a key variable used in data to record and compare the intensities of ionospheric storms. Ionospheric storm occurrences are strongly linked with sudden increases of

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 ...

speed, where solar wind brings energised electrons into the

upper atmosphere Upper atmosphere is a collective term that refers to various layers of the atmosphere of the Earth above the troposphere and corresponding regions of the atmospheres of other planets, and includes: * The mesosphere, which on Earth lies between th ...

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 ...

and contributes to increased TEC. Larger storms form global visibility of

aurora 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 ...

s. Auroras are most commonly seen in the

Arctic Circle The Arctic Circle is one of the two polar circles, and the northernmost of the five major circle of latitude, circles of latitude as shown on maps of Earth at about 66° 34' N. Its southern counterpart is the Antarctic Circle. The Arctic Circl ...

; however, large ionospheric storms allow for them to be visible at somewhat lower

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

s. The most intense ionospheric storm occurred in 1859, commonly named the “

solar storm of 1859 The Carrington Event was the most intense geomagnetic storm in recorded history, peaking on 1–2 September 1859 during solar cycle 10. It created strong auroral displays that were reported globally and caused sparking and even fires in telegr ...

” or the “

Carrington Event The Carrington Event was the most intense geomagnetic storm in recorded history, peaking on 1–2 September 1859 during solar cycle 10. It created strong auroral displays that were reported globally and caused sparking and even fires in telegr ...

.” The Carrington Event was named after

Richard Carrington Richard Christopher Carrington (26 May 1826 – 27 November 1875) was an English astronomer whose 1859 astronomical observations demonstrated the existence of solar flares as well as suggesting their electrical influence upon the Earth and its ...

, an English astronomer who observed the irregular sun activity that occurred during the Carrington Event. The intensity of the storm brought the visibility of the aurora to lower latitudes, and it was reportedly seen in places such as

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

and the

Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...

. Ionospheric storms can happen at any time and location. F-region and D-region ionospheric storms are also considered main categories of ionospheric storms. The F-region storms occur due to sudden increases of energised electrons instilled into Earth's ionosphere. The F-region is the highest region of the ionosphere. Consisting of the F1 and F2 layers, its distance above the Earth's surface is approximately 200–500 km. The duration of these storms are around a day and reoccur every approximately 27.3 days. Most ionospheric abnormalities occur in the F2 and E layers of the ionosphere. D-region storms occur immediately after F-region storms, and are referred to as the “Post-Storm Effect," the duration of it spanning for a week after the F-region storm's occurrence.

Historical occurrences

The largest ionospheric storm occurred during the

Carrington event The Carrington Event was the most intense geomagnetic storm in recorded history, peaking on 1–2 September 1859 during solar cycle 10. It created strong auroral displays that were reported globally and caused sparking and even fires in telegr ...

on August 28, 1859 and caused extensive damages to various parts including the sparking of fires in railway signals and telegraph wires. The substantial density of energised electrons produced by the storm caused these electrical overloads and shortages. Occurrences of storms in the last 35 years have been consolidated and measured in maximum Ap which records the average daily geomagnetic activity during ionospheric storms. There are higher levels of geomagnetic activity with high maximum Ap counts. Ap counts in terms of geomagnetic activity from 0-7 are considered "quiet," 8-15 "unsettled," 16-29 "active," 30-49 "minor storm," 50-99 "major storm," and above 100 classified as a "severe storm." Minor storms in the last 35 years ranging from 30-49 Ap occurred on 13 September 1999 (46), 11 October 2008 (34), 11 March 2011 (37), 9 October 2012 (46) and on 19 February 2014 (43). Major storms ranging from 50-99 Ap occurred on 6 April 2000 (82), 7 April 2000 (74), 11 April 2001 (85), 18 April 2002 (63), 20 April 2002 (70), 22 January 2004 (64), 18 January 2005 (84), 5 April 2010 (55), 9 March 2012 (87), 15 July 2012 (78) and on 1 June 2013 (58). Severe storms equalling or exceeding 100 Ap occurred on 8 February 1986 (202), 9 February 1986 (100), 13 March 1989 (246), 14 March 1989 (158), 17 November 1989 (109), 10 April 1990 (124), 7 April 1995 (100), 31 March 2001 (192), 6 November 2001 (142), 18 August 2003 (108), 29 October 2003 (204), 30 October 2003 (191), 20 November 2003 (150), 27 July 2004 (186), 8 November 2004 (140) and on 10 November 2004 (161). In recent accounts, the St Patrick's Day storms in March 2013 and 2015 caused a strong negative phase in the F2 ionospheric region. The March 2013 and 2015 storms were also long-lasting, spanning for over 6 hours. The June 2015 Southern Hemisphere winter storm had a shorter duration, lasting between 4 and 6 hours, and producing a positive effect in the ionosphere. It is difficult to determine the exact location and time for the occurrences of ionospheric storms, their effects being dependent on season, their varying starting points, compositional changes in the ionosphere and the travelling ionospheric disturbances (TIDs) in relation to

gravity wave In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the oc ...

s having varying impacts on different locations.

Phases of ionospheric storms

In the commencement of an ionospheric storm, due to geomagnetic disturbances in the ionosphere, the storm will become positive for a brief duration. Then, it will become a negative phase storm, and revert to a recovery phase where electron density neutralises.

Positive phase

The positive phase of an ionospheric storm will last for around the first 24 hours. In this phase, electron density in the ionosphere, particularly in higher altitude layers such as F1 and F2 will increase.

Ionisation 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 ...

in the positive phase will be less apparent due to the increase of electron density. Positive phase ionospheric storms have a longer duration and are more prevalent in winter. During the positive phase of large ionospheric storms, the altitude of ionospheric F-region increases, resulting in the massive tongue-shaped plasma anomaly spreading anti-sunward over the

geomagnetic pole The geomagnetic poles are antipodal points where the axis of a best-fitting dipole intersects the surface of Earth. This ''theoretical'' dipole is equivalent to a powerful bar magnet at the center of Earth, and comes closer than any other poi ...

, which can be observed by ground radars, as well as by

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

s and the

GPS The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geol ...

system. Even for the largest

geomagnetic storms 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 and magnetic field structures that originate ...

, such as the 20 November 2003 superstorm, modern

general circulation model A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms for ...

s are able to simulate positive ionospheric anomalies.

Negative phase

The negative phase of an ionospheric storm will occur directly after the storm's positive phase and last one to two days after the positive phase decreases in electron density to "below its quiet time reference level." Negative phases decrease the electron density of the storm. They also span for longer durations and appear more often during summer.

Recovery phase

The recovery phase of the ionospheric storm occurs after the negative phase ends and neutralises the electron density. A time scale of 12 hours to 1 day can be used in accordance with the

Thermosphere The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the ...

Ionosphere General Circulation Model (TIGCM) as a means of calculating the precise time of electron density restabilising post-storm.

Effects on ionospheric layers

The effects of ionospheric storms on different layers in the ionosphere including in the F-region, E-region and D-region vary depending on the magnitude of the storm. F-Region is the most affected layer due to it ranging the highest altitude compared to the E-region and D-region. The D-region is the region with the lowest altitude and will receive the least geomagnetic disturbance.

F-region

The F-region is the highest layer of the ionosphere and inner atmosphere, around 200 km above Earth's surface and spanning around 300 km in total layer altitude. The F2-region of the F-region (highest altitude inner atmospheric layer) will be affected through the decrease of

critical frequency Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine *Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in ...

and maximum usable frequency, which is necessary for high-frequency radio communication. The F-region is affected by the friction of solar wind on the ionospheric boundaries which causes magnetospheric motion that may infiltrate into the ionosphere or exit it, creating disturbances that increase and decrease TEC and electron density. During ionospheric storms, it is more common for "anomalous" increases and decreases of TEC and

electron density Electron density or electronic density is the measure of the probability of an electron being present at an infinitesimal element of space surrounding any given point. It is a scalar quantity depending upon three spatial variables and is typical ...

to occur in the F2-layer. Ionisation density is also affected in the F-region, decreasing as the height increases, and as ionisation density increases, atoms lose electrons and therefore lower altitudes lose electron density. The lower layers of the F-region such as the F1-layer have higher amounts of ionisation and less electron density.

E-region

The E-region is the middle layer of the ionosphere, approximately 100 km above the Earth's surface, spanning around 100 km up. Effects on the E-region are mainly associated with the high latitudes of the layer, where more severe geomagnetic disturbances occur. Ionisation in this layer is predominantly derived from the particle precipitation in auroras. Due to its lower latitude, there is greater ionisation density compared to that of the F-region, and less electron density. Increased conductivity of

currents Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (hy ...

is caused by the

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

electric fields of the

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 ...

that run down the lines of the

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 ...

in the E-region. The increased conductivity is also from the effects of the ionospheric storm. There is also a maximisation in the E-region of the transfer of energy from plasma to neutral particles which promotes "frictional heating" and is used as a heat source for the thermosphere.

D-region

The D-region is the lowest layer of the ionosphere, approximately 60 km above the Earth's surface and its layer's altitude spanning around 30–40 km. The top of the D-region is around 90–100 km above the Earth's surface. When ionospheric storms occur, there is enhanced ionisation of electrons that happens in the D-region and causes a decline in day-night asymmetry (DLPT depth). DLPT depth is calculated by subtracting average day rate by average night rate and dividing it by the average of the rates. The DLPT depth decreases as Ap increases in the D-layer.

Impacts

Radio communications

There can be strong disturbances to telecommunications in the event of an ionospheric storm, where in middle and high altitudes, radio communications are considered “ineffective.” This is due to

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 being found in the ionosphere where the sudden increase of solar wind and energised electrons will interfere. The impacts of disturbances related to radio communications can include temporary blackouts of signal to radio wave-based technology such as televisions, radios, and cordless phones. Global impacts vary, including the detriment of digital broadcasting and the displaying of information through radio-communication technologies which may temporarily eliminate the use of certain technologies.

Aircraft and electrical systems

Aircraft passengers and crew receive a higher dose of radiation during an ionospheric storm, relative to people at sea level. Flight altitudes are usually 10 km or more, so when an ionospheric storm occurs during the flight, people on the plane will potentially gain an approximate 0.1% chance of developing a lethal cancer during their lifetime. The plane when flying at a 10 km or above altitude will have around 300 times more exposure to ionised radiation than on sea level. The energised particles produced by the ionospheric storm can also potentially cause damage and disrupt

microelectronic Microelectronics is a subfield of electronics. As the name suggests, microelectronics relates to the study and manufacture (or microfabrication) of very small electronic designs and components. Usually, but not always, this means micrometre- ...

circuitry due to single-event error (SEE), when the energised particles interconnect with the

semiconductor device A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its conductivit ...

and causes system failure. The short-circuiting of aircraft electrical equipment can be a distraction to the aircrew, which can be a safety hazard.

Satellites

Solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s on satellites may be damaged or destroyed in ionospheric storms, which can hinder the transmission of signals.

Climate

Earthward solar winds and excessive radiation produced from it has limited effect on the climate. The radiation emitted by solar wind only reaches the highest layers of the Earth's atmosphere, including the ionosphere. There are however reports of a possible impact on lower layers of the atmosphere. It is recorded that the increase of solar wind during March 2012 in the United States coincided with the heat waves that occurred at the time. A statistical connection between the occurrence of heavy

floods A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

and ionospheric storms caused by high-speed

streams (HSSs) has been also reported. The enhanced energy deposition into the

auroral 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 polar regions of Earth, high-latitude ...

during HSSs is suggested to generate downward-propagating atmospheric

gravity waves In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the oc ...

. The excited

reach lower atmosphere, triggering an

instability In dynamical systems instability means that some of the outputs or internal states increase with time, without bounds. Not all systems that are not stable are unstable; systems can also be marginally stable or exhibit limit cycle behavior. ...

in the

troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...

and leading to excessive rainfall.

GPS and GNSS systems

Due to the disturbances of signals in the ionosphere caused by ionospheric storms, GPS systems are drastically affected. In the late 20th and 21st centuries, GPS signals were incorporated within various phones, so the commonality of its use has greatly increased since its release. It is a significant piece of technology that is almost entirely affected as it serves the purpose of displaying directions, which can prevent people from being able to tell directions. Directional equipment like Global Navigation Satellite Services (GNSS) is also used in aircraft. This system can be compromised by radiation damage on satellites and solar cells all of which are needed for this navigation system to work. When an aircraft loses access to GNSS in the event of an ionospheric storm, backup aircraft procedures are available.

Storm detection technology

During the Carrington Event in 1859 where there were only a limited number of available measuring technologies, the full extent of the impacts could not be precisely recorded apart from recounts in newspaper articles written in 1859. In the late 20th and early 21st century, forecasting technology has been improved. This technology allows meteorologists to detect the highest frequency that can be vertically returned 24 hours in advance with accuracy of 8-13% periods with limited disturbance. PropMan, created by K. Davies in the early 1970s is a program that contains the ionospheric prediction code (IONSTORM), to forecast maximum usable frequencies (MUFs) during ionospheric storms when F-region communication frequencies are negated.

References

{{Reflist Ionosphere