What Creates the Van Allen Belts Apex

Zone of energetic charged particles around the planet Globe

A
Van Allen radiation belt
is a zone of energetic charged particles, almost of which originate from the solar current of air, 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 is credited with their discovery.^[1]
Earth’due south two primary belts extend from an altitude of about 640 to 58,000 km (400 to 36,040 mi)^[ii]
in a higher place the surface, in which region radiation levels vary. Most of the particles that course the belts are thought to come up from solar wind and other particles by cosmic rays.^[3]
By trapping the solar air current, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.

The belts are in the inner region of Earth’s magnetic field. The belts trap energetic electrons and protons. Other nuclei, such as alpha particles, are less prevalent. The belts endanger satellites, which must have their sensitive components protected with adequate shielding if they spend significant time near that zone. In 2013, the Van Allen Probes detected a transient, 3rd radiation chugalug, which persisted for iv weeks.^[iv]
Apollo Astronauts going through the Van Allen Belts received a very low and not-harmful dose of radiation.

Discovery

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Kristian Birkeland, Carl Størmer, Nicholas Christofilos, and Enrico Medi had investigated the possibility of trapped charged particles before the Space Age.^[5]
Explorer 1 and Explorer three confirmed the being of the belt in early 1958 under James Van Allen at the University of Iowa.^[1]
The trapped radiation was first mapped by Explorer iv, Pioneer 3, and Luna ane.

The term
Van Allen belts
refers specifically to the radiations belts surrounding Earth; all the same, similar radiations belts accept been discovered effectually other planets. The Sun does not support long-term radiation belts, every bit information technology lacks a stable, global dipole field. The Earth’southward temper limits the belts’ particles to regions above 200–1,000 km,^[six]
(124–620 miles) while the belts exercise not extend by viii Earth radii
R_E
.^[6]
The belts are confined to a volume which extends nigh 65°^[vi]
on either side of the angelic equator.

Inquiry

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The NASA Van Allen Probes mission aims at agreement (to the point of predictability) how populations of relativistic electrons and ions in space class or modify in response to changes in solar activity and the solar wind. NASA Institute for Advanced Concepts–funded studies have proposed magnetic scoops to collect antimatter that naturally occurs in the Van Allen belts of Earth, although simply about 10 micrograms of antiprotons are estimated to exist in the entire belt.^[7]

The Van Allen Probes mission successfully launched on August thirty, 2012. The primary mission was scheduled to terminal two years with expendables expected to last four. The probes were deactivated in 2019 afterward running out of fuel and are expected to deorbit during the 2030s.^[8]
NASA’south Goddard Space Flight Eye manages the Living With a Star program—of which the Van Allen Probes are a project, forth with Solar Dynamics Observatory (SDO). The Applied Physics Laboratory is responsible for the implementation and instrument management for the Van Allen Probes.^[9]

Radiation belts exist around other planets and moons in the solar system that have magnetic fields powerful enough to sustain them. To date, most of these radiation belts have been poorly mapped. The Voyager Plan (namely Voyager 2) only nominally confirmed the existence of like belts around Uranus and Neptune.

Geomagnetic storms can cause electron density to increase or decrease relatively quickly (i.e., approximately one 24-hour interval or less). Longer-timescale processes determine the overall configuration of the belts. After electron injection increases electron density, electron density is often observed to decay exponentially. Those decay time constants are called “lifetimes.” Measurements from the Van Allen Probe B’s Magnetic Electron Ion Spectrometer (MagEIS) evidence long electron lifetimes (i.e., longer than 100 days) in the inner belt; short electron lifetimes of around 1 or two days are observed in the “slot” betwixt the belts; and energy-dependent electron lifetimes of roughly five to 20 days are found in the outer belt.^[ten]

Inner belt

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The inner Van Allen Belt extends typically from an altitude of 0.ii to 2 Earth radii (L values of ane to 3) or ane,000 km (620 mi) to 12,000 km (7,500 mi) above the Earth.^[3]
[11]
In certain cases, when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly, the inner purlieus may decline to roughly 200 km^[12]
to a higher place the World’s surface. The inner chugalug contains high concentrations of electrons in the range of hundreds of keV and energetic protons with energies exceeding 100 MeV—trapped by the relatively strong magnetic fields in the region (as compared to the outer belt).^[thirteen]

It is believed that proton energies exceeding 50 MeV in the lower belts at lower altitudes are the upshot of the beta decay of neutrons created by catholic ray collisions with nuclei of the upper atmosphere. The source of lower energy protons is believed to be proton improvidence, due to changes in the magnetic field during geomagnetic storms.^[14]

Due to the slight kickoff of the belts from Earth’s geometric center, the inner Van Allen chugalug makes its closest approach to the surface at the Due south Atlantic Anomaly.^[15]
[16]

In March 2014, a pattern resembling “zebra stripes” was observed in the radiation belts by the Radiation Belt Tempest Probes Ion Composition Experiment (RBSPICE) onboard Van Allen Probes. The initial theory proposed in 2014 was that—due to the tilt in World’south magnetic field axis—the planet’s rotation generated an oscillating, weak electrical field that permeates through the unabridged inner radiation belt.^[17]
A 2016 written report instead concluded that the zebra stripes were an imprint of ionospheric winds on radiation belts.^[eighteen]

Outer belt

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The outer chugalug consists mainly of high-energy (0.1–10 MeV) electrons trapped by the World’s magnetosphere. Information technology is more variable than the inner belt, as it is more hands influenced by solar activity. It is most toroidal in shape, beginning at an distance of 3 Earth radii and extending to x Earth radii (R_E
)—xiii,000 to 60,000 kilometres (8,100 to 37,300 mi) above the Earth’s surface. Its greatest intensity is usually effectually four to 5
R_E
. The outer electron radiations belt is generally produced by the inward radial diffusion^[19]
[xx]
and local acceleration^[21]
due to transfer of energy from whistler-way plasma waves to radiation chugalug electrons. Radiation belt electrons are also constantly removed by collisions with Earth’s temper,^[21]
losses to the magnetopause, and their outward radial diffusion. The gyroradii of energetic protons would be large plenty to bring them into contact with the Earth’s atmosphere. Within this chugalug, the electrons have a high flux and at the outer edge (close to the magnetopause), where geomagnetic field lines open into the geomagnetic “tail”, the flux of energetic electrons can driblet to the depression interplanetary levels within almost 100 km (62 mi)—a decrease by a factor of 1,000.

In 2014, it was discovered that the inner border of the outer belt is characterized by a very sharp transition, below which highly relativistic electrons (> 5MeV) cannot penetrate.^[22]
The reason for this shield-like behavior is non well understood.

The trapped particle population of the outer belt is varied, containing electrons and various ions. Most of the ions are in the class of energetic protons, just a certain percentage are alpha particles and O⁺
oxygen ions—similar to those in the ionosphere only much more energetic. This mixture of ions suggests that ring current particles probably originate from more than ane source.

The outer chugalug is larger than the inner belt, and its particle population fluctuates widely. Energetic (radiation) particle fluxes can increase and subtract dramatically in response to geomagnetic storms, which are themselves triggered by magnetic field and plasma disturbances produced past the Sun. The increases are due to storm-related injections and acceleration of particles from the tail of the magnetosphere.

On Feb 28, 2013, a 3rd radiation belt—consisting of loftier-energy ultrarelativistic charged particles—was reported to be discovered. In a news conference by NASA’south Van Allen Probe squad, information technology was stated that this 3rd belt is a product of coronal mass ejection from the Sun. It has been represented as a split creation which splits the Outer Belt, like a knife, on its outer side, and exists separately every bit a storage container of particles for a calendar month’south time, before merging one time again with the Outer Belt.^[23]

The unusual stability of this 3rd, transient belt has been explained every bit due to a ‘trapping’ by the World’due south magnetic field of ultrarelativistic particles as they are lost from the second, traditional outer chugalug. While the outer zone, which forms and disappears over a mean solar day, is highly variable due to interactions with the atmosphere, the ultrarelativistic particles of the third belt are idea not to scatter into the atmosphere, every bit they are too energetic to interact with atmospheric waves at depression latitudes.^[24]
This absence of scattering and the trapping allows them to persist for a long time, finally only being destroyed by an unusual event, such as the shock wave from the Dominicus.

Flux values

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In the belts, at a given signal, the flux of particles of a given energy decreases sharply with energy.

At the magnetic equator, electrons of energies exceeding 5000 keV (resp. five MeV) have omnidirectional fluxes ranging from i.ii×10⁶
(resp. 3.7×10^four) up to nine.four×10⁹
(resp. two×10⁷) particles per square centimeter per 2d.

The proton belts comprise protons with kinetic energies ranging from about 100 keV, which tin penetrate 0.6 µm of pb, to over 400 MeV, which can penetrate 143 mm of lead.^[25]

Most published flux values for the inner and outer belts may not show the maximum probable flux densities that are possible in the belts. In that location is a reason for this discrepancy: the flux density and the location of the peak flux is variable, depending primarily on solar activity, and the number of spacecraft with instruments observing the belt in existent time has been express. The Earth has not experienced a solar storm of Carrington event intensity and duration, while spacecraft with the proper instruments accept been available to observe the event.

Radiations levels in the belts would exist dangerous to humans if they were exposed for an extended menstruation of time. The Apollo missions minimised hazards for astronauts past sending spacecraft at loftier speeds through the thinner areas of the upper belts, bypassing inner belts completely, except for the Apollo xiv mission where the spacecraft traveled through the heart of the trapped radiations belts.^{[xv]
[26]
[27]
[28]}

• Flux values, normal solar conditions

• 

  AP8 MIN omnidirectional proton flux ≥ 100 keV

• 

  AP8 MIN omnidirectional proton flux ≥ 1 MeV

• 

  AP8 MIN omnidirectional proton flux ≥ 400 MeV

Antimatter confinement

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In 2011, a report confirmed earlier speculation that the Van Allen chugalug could confine antiparticles. The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment detected levels of antiprotons orders of magnitude higher than are expected from normal particle decays while passing through the South Atlantic Bibelot. This suggests the Van Allen belts confine a pregnant flux of antiprotons produced by the interaction of the Earth’s upper atmosphere with cosmic rays.^[29]
The energy of the antiprotons has been measured in the range from 60 to 750 MeV.

Inquiry funded by the NASA Constitute for Advanced Concepts concluded that harnessing these antiprotons for spacecraft propulsion would be viable. Researchers believed that this approach would have advantages over antiproton generation at CERN, considering collecting the particles in situ eliminates transportation losses and costs. Jupiter and Saturn are also possible sources, but the Earth belt is the nearly productive. Jupiter is less productive than might be expected due to magnetic shielding from catholic rays of much of its atmosphere. In 2019, CMS^{[
definition needed
]}
announced that the construction of a device that would be capable of collecting these particles has already begun.<sup>[
dubious

– talk over
]</sup>
NASA will use this device to collect these particles and ship them to institutes all around the world for further test. These so-called “antimatter-containers” could exist used for industrial purpose as well in the future.^[30]

Implications for space travel

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Spacecraft travelling beyond low World orbit enter the zone of radiation of the Van Allen belts. Beyond the belts, they confront additional hazards from cosmic rays and solar particle events. A region between the inner and outer Van Allen belts lies at 2 to 4 Earth radii and is sometimes referred to as the “safe zone”.^[31]
[32]

Solar cells, integrated circuits, and sensors can be damaged by radiation. Geomagnetic storms occasionally damage electronic components on spacecraft. Miniaturization and digitization of electronics and logic circuits have made satellites more than vulnerable to radiation, as the total electric charge in these circuits is now modest enough and then as to be comparable with the charge of incoming ions. Electronics on satellites must be hardened confronting radiation to operate reliably. The Hubble Infinite Telescope, among other satellites, ofttimes has its sensors turned off when passing through regions of intense radiation.^[33]
A satellite shielded by 3 mm of aluminium in an elliptic orbit (200 by 20,000 miles (320 by 32,190 km)) passing the radiations belts volition receive well-nigh ii,500 rem (25 Sv) per twelvemonth. (For comparison, a full-torso dose of v Sv is deadly.) Virtually all radiations will be received while passing the inner belt.^[34]

The Apollo missions marked the first event where humans traveled through the Van Allen belts, which was ane of several radiations hazards known by mission planners.^[35]
The astronauts had low exposure in the Van Allen belts due to the short period of fourth dimension spent flying through them.^[27]
[36]

Astronauts’ overall exposure was actually dominated past solar particles once outside Earth’s magnetic field. The total radiations received by the astronauts varied from mission-to-mission but was measured to be between 0.16 and ane.14 rads (1.vi and 11.4 mGy), much less than the standard of 5 rem (50 mSv)^[c]
per year set by the United States Diminutive Energy Commission for people who piece of work with radioactivity.^[35]

Causes

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It is by and large understood that the inner and outer Van Allen belts event from different processes. The inner belt—consisting mainly of energetic protons—is the product of the disuse of so-called “albedo” neutrons, which are themselves the result of cosmic ray collisions in the upper atmosphere. The outer belt consists mainly of electrons. They are injected from the geomagnetic tail following geomagnetic storms, and are afterwards energized through wave-particle interactions.

In the inner belt, particles that originate from the Sun are trapped in the Earth’s magnetic field. Particles screw along the magnetic lines of flux every bit they move “latitudinally” along those lines. As particles movement toward the poles, the magnetic field line density increases, and their “latitudinal” velocity is slowed and can be reversed—reflecting the particles and causing them to bounciness back and forth between the Earth’s poles.^[37]
In add-on to the screw about and motion along the flux lines, the electrons movement slowly in an eastward direction, while the ions move w.

A gap betwixt the inner and outer Van Allen belts—sometimes called safe zone or safe slot—is caused by the Very Low Frequency (VLF) waves, which scatter particles in pitch angle, which results in the gain of particles to the atmosphere. Solar outbursts tin pump particles into the gap, but they drain over again in a affair of days. The radio waves were originally thought to be generated past turbulence in the radiation belts, but recent piece of work by James L. Green of the Goddard Infinite Flight Center—comparing maps of lightning activeness collected past the Microlab one spacecraft with information on radio waves in the radiation-belt gap from the Paradigm spacecraft—suggests that they are really generated by lightning inside World’s atmosphere. The generated radio waves strike the ionosphere at the right angle to pass through only at high latitudes, where the lower ends of the gap approach the upper temper. These results are nonetheless under scientific debate.

Proposed removal

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Draining the charged particles from the Van Allen belts would open upward new orbits for satellites and make travel safer for astronauts.^[38]

High Voltage Orbiting Long Tether, or HiVOLT, is a concept proposed by Russian physicist Five. V. Danilov and farther refined past Robert P. Hoyt and Robert L. Forrard for draining and removing the radiation fields of the Van Allen radiation belts^[39]
that surroundings the Earth.^[forty]

Some other proposal for draining the Van Allen belts involves beaming very-low-frequency (VLF) radio waves from the ground into the Van Allen belts.^[41]

Draining radiation belts around other planets has also been proposed, for instance, before exploring Europa, which orbits within Jupiter’s radiations belt.^[42]

Equally of 2014, it remains uncertain if there are whatsoever negative unintended consequences to removing these radiation belts.^[38]

Run into also

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• Dipole model of the Earth’south magnetic field
• L-beat
• Listing of artificial radiations belts
• List of plasma (physics) articles
• Infinite weather condition

Explanatory notes

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Citations

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Boosted sources

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• Adams, L.; Daly, E. J.; Harboe-Sorensen, R.; Holmes-Siedle, A. G.; Ward, A. K.; Bull, R. A. (December 1991). “Measurement of SEU and total dose in geostationary orbit under normal and solar flare conditions”.
  IEEE Transactions on Nuclear Science.
  38
  (six): 1686–1692. Bibcode:1991ITNS…38.1686A. doi:10.1109/23.124163. OCLC 4632198117.
  
• Holmes-Siedle, Andrew; Adams, Len (2002).
  Handbook of Radiation Effects
  (second ed.). Oxford; New York: Oxford University Press. ISBN978-0-xix-850733-8. LCCN 2001053096. OCLC 47930537.
  
• Shprits, Yuri Y.; Elkington, Scott R.; Meredith, Nigel P.; Subbotin, Dmitriy A. (November 2008). “Review of modeling of losses and sources of relativistic electrons in the outer radiations chugalug”.
  Journal of Atmospheric and Solar-Terrestrial Physics.
  70
  (14).
  
  Part I: Radial transport, pp. 1679–1693, doi:10.1016/j.jastp.2008.06.008; Function II: Local acceleration and loss, pp. 1694–1713, doi:ten.1016/j.jastp.2008.06.014.

External links

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• An explanation of the belts by David P. Stern and Mauricio Peredo
• Background: Trapped particle radiation models—Introduction to the trapped radiation belts by SPENVIS
• SPENVIS—Space Surround, Effects, and Educational activity System—Gateway to the SPENVIS orbital dose adding software
• The Van Allen Probes Web Site Johns Hopkins University Applied Physics Laboratory