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68-401: Earth's two main belts extend from an altitude of about 640 to 58,000 km (400 to 36,040 mi) 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

136-512: A 'trapping' by the Earth's magnetic field of ultrarelativistic particles as they are lost from the second, traditional outer belt. While the outer zone, which forms and disappears over a day, is highly variable due to interactions with the atmosphere, the ultrarelativistic particles of the third belt are thought not to scatter into the atmosphere, as they are too energetic to interact with atmospheric waves at low latitudes. This absence of scattering and

204-447: A higher heart rate, and adjusting its blood chemistry. It can take days or weeks to adapt to high altitude. However, above 8,000 metres (26,000 ft), (in the " death zone "), altitude acclimatization becomes impossible. There is a significantly lower overall mortality rate for permanent residents at higher altitudes. Additionally, there is a dose response relationship between increasing elevation and decreasing obesity prevalence in

272-563: A news conference by NASA's Van Allen Probe team, it was stated that this third belt is a product of coronal mass ejection from the Sun. It has been represented as a separate creation which splits the Outer Belt, like a knife, on its outer side, and exists separately as a storage container of particles for a month's time, before merging once again with the Outer Belt. The unusual stability of this third, transient belt has been explained as due to

340-515: A stable, global dipole field. The Earth's atmosphere limits the belts' particles to regions above 200–1,000 km, (124–620 miles) while the belts do not extend past 8 Earth radii R E . The belts are confined to a volume which extends about 65 ° on either side of the celestial equator . The NASA Van Allen Probes mission aims at understanding (to the point of predictability) how populations of relativistic electrons and ions in space form or change in response to changes in solar activity and

408-537: A very low and harmless dose of radiation. In 2013, the Van Allen Probes detected a transient, third radiation belt, which persisted for four weeks. Kristian Birkeland , Carl Størmer , Nicholas Christofilos , and Enrico Medi had investigated the possibility of trapped charged particles in 1895, forming a theoretical basis for the formation of radiation belts. The second Soviet satellite Sputnik 2 which had detectors designed by Sergei Vernov , followed by

476-407: Is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometry, geographical survey, sport, or atmospheric pressure). Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation

544-542: Is an area where Earth 's inner Van Allen radiation belt comes closest to Earth's surface , dipping down to an altitude of 200 kilometres (120 mi). This leads to an increased flux of energetic particles in this region and exposes orbiting satellites (including the ISS ) to higher-than-usual levels of ionizing radiation . The effect is caused by the non- concentricity of Earth with its magnetic dipole and has been observed to be increasing in intensity recently. The SAA

612-421: Is characterized by a very sharp transition, below which highly relativistic electrons (> 5MeV) cannot penetrate. The reason for this shield-like behavior is not well understood. The trapped particle population of the outer belt is varied, containing electrons and various ions. Most of the ions are in the form of energetic protons, but a certain percentage are alpha particles and O oxygen ions—similar to those in

680-410: Is due to two competing physical effects: gravity, which causes the air to be as close as possible to the ground; and the heat content of the air, which causes the molecules to bounce off each other and expand. The temperature profile of the atmosphere is a result of an interaction between radiation and convection . Sunlight in the visible spectrum hits the ground and heats it. The ground then heats

748-472: Is known as the adiabatic lapse rate , which is approximately 9.8 °C per kilometer (or 5.4 °F [3.0 °C] per 1000 feet) of altitude. The presence of water in the atmosphere complicates the process of convection. Water vapor contains latent heat of vaporization . As air rises and cools, it eventually becomes saturated and cannot hold its quantity of water vapor. The water vapor condenses (forming clouds ), and releases heat, which changes

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816-781: Is of great significance to astronomical satellites and other spacecraft that orbit the Earth at several hundred kilometers altitude; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong ionizing radiation, caused by the trapped protons in the inner Van Allen belt. Measurements on Space Shuttle flight STS-94 have ascertained that absorbed dose rates from charged particles have extended from 112 to 175 μGy/day, with dose equivalent rates ranging from 264.3 to 413 μSv/day. The International Space Station , orbiting with an inclination of 51.6°, requires extra shielding to deal with this problem. The Hubble Space Telescope does not take observations with its sensitive UV detectors while passing through

884-580: Is often preferred for this usage. In aviation, altitude is typically measured relative to mean sea level or above ground level to ensure safe navigation and flight operations. In geometry and geographical surveys, altitude helps create accurate topographic maps and understand the terrain's elevation. For high-altitude trekking and sports, knowing and adapting to altitude is vital for performance and safety. Higher altitudes mean reduced oxygen levels, which can lead to altitude sickness if proper acclimatization measures are not taken. Vertical distance measurements in

952-424: Is slowed and can be reversed, deflecting the particles back towards the equatorial region, causing them to bounce back and forth between the Earth's poles. In addition to both spiralling around and moving along the flux lines, the electrons drift slowly in an eastward direction, while the protons drift westward. The gap between the inner and outer Van Allen belts is sometimes called the "safe zone" or "safe slot", and

1020-605: Is the location of medium Earth orbits . The gap is caused by the VLF radio waves , which scatter particles in pitch angle , which adds new ions to the atmosphere. Solar outbursts can also dump particles into the gap, but those drain out in a matter of days. The VLF radio waves were previously thought to be generated by turbulence in the radiation belts, but recent work by J.L. Green of the Goddard Space Flight Center compared maps of lightning activity collected by

1088-491: Is the near-Earth region where Earth's magnetic field is weakest relative to an idealized Earth-centered dipole field. The area of the SAA is confined by the intensity of Earth's magnetic field at less than 32,000 nanotesla at sea level, which corresponds to the dipolar magnetic field at ionospheric altitudes. However, the field itself varies in intensity as a gradient. The Van Allen radiation belts are symmetric about

1156-444: Is the process of convection . Convection comes to equilibrium when a parcel of air at a given altitude has the same density as its surroundings. Air is a poor conductor of heat, so a parcel of air will rise and fall without exchanging heat. This is known as an adiabatic process , which has a characteristic pressure-temperature curve. As the pressure gets lower, the temperature decreases. The rate of decrease of temperature with elevation

1224-508: Is the transition altitude). When flying at a flight level, the altimeter is always set to standard pressure (29.92  inHg or 1013.25  hPa ). On the flight deck, the definitive instrument for measuring altitude is the pressure altimeter , which is an aneroid barometer with a front face indicating distance (feet or metres) instead of atmospheric pressure . There are several types of altitude in aviation: These types of altitude can be explained more simply as various ways of measuring

1292-530: The Microlab 1 spacecraft with data on radio waves in the radiation-belt gap from the IMAGE spacecraft; the results suggest that the radio waves are actually generated by lightning within Earth's atmosphere. The generated radio waves strike the ionosphere at the correct angle to pass through only at high latitudes, where the lower ends of the gap approach the upper atmosphere. These results are still being debated in

1360-548: The United States Atomic Energy Commission for people who work with radioactivity. It is generally understood that the inner and outer Van Allen belts result from different processes. The inner belt is mainly composed of energetic protons produced from the decay of so-called neutrons , which are themselves the result of cosmic ray collisions in the upper atmosphere. The outer Van Allen belt consists mainly of electrons. They are injected from

1428-561: The failures of the Globalstar network's satellites in 2007. The PAMELA experiment, while passing through the SAA, detected antiproton levels that were orders of magnitude higher than expected. This suggests the Van Allen belt confines antiparticles produced by the interaction of the Earth's upper atmosphere with cosmic rays . NASA has reported that modern laptop computers have crashed when Space Shuttle flights passed through

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1496-441: The ionosphere but much more energetic. This mixture of ions suggests that ring current particles probably originate from more than one source. The outer belt is larger than the inner belt, and its particle population fluctuates widely. Energetic (radiation) particle fluxes can increase and decrease dramatically in response to geomagnetic storms , which are themselves triggered by magnetic field and plasma disturbances produced by

1564-435: The troposphere (up to approximately 11 kilometres (36,000 ft) of altitude) in the Earth's atmosphere undergoes notable convection; in the stratosphere , there is little vertical convection. Medicine recognizes that altitudes above 1,500 metres (4,900 ft) start to affect humans, and there is no record of humans living at extreme altitudes above 5,500–6,000 metres (18,000–19,700 ft) for more than two years. As

1632-455: The "down" direction are commonly referred to as depth . The term altitude can have several meanings, and is always qualified by explicitly adding a modifier (e.g. "true altitude"), or implicitly through the context of the communication. Parties exchanging altitude information must be clear which definition is being used. Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as

1700-695: The 2030s. NASA's Goddard Space Flight Center manages the Living With a Star program—of which the Van Allen Probes were a project, along with Solar Dynamics Observatory (SDO). The Applied Physics Laboratory was responsible for the implementation and instrument management for the Van Allen Probes. 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 Program (namely Voyager 2 ) only nominally confirmed

1768-538: The Earth called the African large low-shear velocity province . The position of the anomaly can be that of the maximum magnetic flux or that of the centroid of the flux, which is less sensitive to sampling noise and more representative of the feature as a whole. In January 2021, the centroid was located near 26°37′S 49°04′W  /  26.61°S 49.06°W  / -26.61; -49.06 and drifting about 0.23°S 0.34°W per year. The South Atlantic Anomaly

1836-405: The Earth's atmosphere. Within this belt, 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 drop to the low interplanetary levels within about 100 km (62 mi)—a decrease by a factor of 1,000. In 2014, it was discovered that the inner edge of the outer belt

1904-477: The Earth's magnetic axis, which is tilted with respect to the Earth's rotational axis by an angle of approximately 11°. The intersection between the magnetic and rotation axes of the Earth is located not at the Earth's center, but some 450 to 500 km (280 to 310 mi) away. Because of this asymmetry, the inner Van Allen belt is closest to the Earth's surface over the south Atlantic Ocean where it dips down to 200 km (120 mi) in altitude, and farthest from

1972-496: The Earth's surface over the north Pacific Ocean. If Earth's magnetism is represented by a bar magnet of small size but strong intensity (" magnetic dipole "), the SAA variation can be illustrated by placing the magnet not in the plane of the Equator, but some small distance North, shifted more or less in the direction of Singapore . As a result, over northern South America and the south Atlantic, near Singapore's antipodal point ,

2040-519: The Earth's surface. Its greatest intensity is usually around 4 to 5 R E . The outer electron radiation belt is mostly produced by inward radial diffusion and local acceleration due to transfer of energy from whistler-mode plasma waves to radiation belt electrons. Radiation belt electrons are also constantly removed by collisions with Earth's atmosphere, losses to the magnetopause , and their outward radial diffusion. The gyroradii of energetic protons would be large enough to bring them into contact with

2108-528: The Earth. Another proposal for draining the Van Allen belts involves beaming very-low-frequency (VLF) radio waves from the ground into the Van Allen belts. Draining radiation belts around other planets has also been proposed, for example, before exploring Europa , which orbits within Jupiter 's radiation belt. As of 2024, it remains uncertain if there are any negative unintended consequences to removing these radiation belts. Altitude Altitude

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2176-497: The Earth. In certain cases, when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly , the inner boundary may decline to roughly 200 km above the Earth's surface. The inner belt 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

2244-477: The SAA. Passing through the anomaly caused false alarms on Skylab Apollo Telescope Mount 's solar flare sensor. Astronauts are also affected by this region, which is said to be the cause of peculiar "shooting stars" ( phosphenes ) seen in the visual field of astronauts, an effect termed cosmic ray visual phenomena . Passing through the South Atlantic Anomaly is thought to be the reason for

2312-435: The Sun. The increases are due to storm-related injections and acceleration of particles from the tail of the magnetosphere. Another cause of variability of the outer belt particle populations is the wave-particle interactions with various plasma waves in a broad range of frequencies. On February 28, 2013, a third radiation belt—consisting of high-energy ultrarelativistic charged particles—was reported to be discovered. In

2380-613: The US satellites Explorer 1 and Explorer 3 , confirmed the existence of the belt in early 1958, later named after James Van Allen from the University of Iowa . The trapped radiation was first mapped by Explorer 4 , Pioneer 3 , and Luna 1 . The term Van Allen belts refers specifically to the radiation belts surrounding Earth; however, similar radiation belts have been discovered around other planets . The Sun does not support long-term radiation belts, as it lacks

2448-597: The United States. In addition, the recent hypothesis suggests that high altitude could be protective against Alzheimer's disease via action of erythropoietin, a hormone released by kidney in response to hypoxia. However, people living at higher elevations have a statistically significant higher rate of suicide. The cause for the increased suicide risk is unknown so far. For athletes, high altitude produces two contradictory effects on performance. For explosive events (sprints up to 400 metres, long jump , triple jump )

2516-584: The Van Allen Probe B's Magnetic Electron Ion Spectrometer (MagEIS) show long electron lifetimes (i.e., longer than 100 days) in the inner belt; short electron lifetimes of around one or two days are observed in the "slot" between the belts; and energy-dependent electron lifetimes of roughly five to 20 days are found in the outer belt. The inner Van Allen Belt extends typically from an altitude of 0.2 to 2 Earth radii ( L values of 1.2 to 3) or 1,000 km (620 mi) to 12,000 km (7,500 mi) above

2584-490: The Van Allen belts confine a significant flux of antiprotons produced by the interaction of the Earth's upper atmosphere with cosmic rays. The energy of the antiprotons has been measured in the range from 60 to 750 MeV. The very high energy released in antimatter annihilation has led to proposals to harness these antiprotons for spacecraft propulsion. The concept relies on the development of antimatter collectors and containers. Spacecraft travelling beyond low Earth orbit enter

2652-424: The Van Allen belts due to the short period of time spent flying through them. Astronauts' overall exposure was actually dominated by solar particles once outside Earth's magnetic field. The total radiation received by the astronauts varied from mission-to-mission but was measured to be between 0.16 and 1.14 rads (1.6 and 11.4  mGy ), much less than the standard of 5 rem (50 mSv) per year set by

2720-414: The air at the surface. If radiation were the only way to transfer heat from the ground to space, the greenhouse effect of gases in the atmosphere would keep the ground at roughly 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height. However, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward. This

2788-441: The altitude increases, atmospheric pressure decreases, which affects humans by reducing the partial pressure of oxygen . The lack of oxygen above 2,400 metres (8,000 ft) can cause serious illnesses such as altitude sickness , high altitude pulmonary edema , and high altitude cerebral edema . The higher the altitude, the more likely are serious effects. The human body can adapt to high altitude by breathing faster, having

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2856-439: The altitude: The Earth's atmosphere is divided into several altitude regions. These regions start and finish at varying heights depending on season and distance from the poles. The altitudes stated below are averages: The Kármán line , at an altitude of 100 kilometres (62 mi) above sea level , by convention defines represents the demarcation between the atmosphere and space . The thermosphere and exosphere (along with

2924-736: The anomaly. In October 2012, the SpaceX CRS-1 Dragon spacecraft attached to the International Space Station experienced a transient problem as it passed through the anomaly. The SAA is believed to have started a series of events leading to the destruction of the Hitomi , Japan's most powerful X-ray observatory. The anomaly transiently disabled a direction-finding mechanism, causing the satellite to rely solely on gyroscopes that were not working properly, after which it spun out of control, losing its solar panels in

2992-856: The challenge of maintaining body heat in cold temperatures, due to their small volume to surface area ratio. As oxygen is used as a source of metabolic heat production, the hypobaric hypoxia at high altitudes is problematic. There is also a general trend of smaller body sizes and lower species richness at high altitudes, likely due to lower oxygen partial pressures. These factors may decrease productivity in high altitude habitats, meaning there will be less energy available for consumption, growth, and activity. However, some species, such as birds, thrive at high altitude. Birds thrive because of physiological features that are advantageous for high-altitude flight. South Atlantic Anomaly 26°37′S 49°04′W  /  26.61°S 49.06°W  / -26.61; -49.06 The South Atlantic Anomaly ( SAA )

3060-532: The entire inner radiation belt. A 2016 study instead concluded that the zebra stripes were an imprint of ionospheric winds on radiation belts. The outer belt consists mainly of high-energy (0.1–10  MeV ) electrons trapped by the Earth's magnetosphere. It is more variable than the inner belt, as it is more easily influenced by solar activity. It is almost toroidal in shape, beginning at an altitude of 3 Earth radii and extending to 10 Earth radii ( R E )—13,000 to 60,000 kilometres (8,100 to 37,300 mi) above

3128-451: The existence of similar belts around Uranus and Neptune . Geomagnetic storms can cause electron density to increase or decrease relatively quickly (i.e., approximately one day 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

3196-487: The geomagnetic field continues to weaken, the inner Van Allen belt gets closer to the Earth, with a commensurate enlargement of the SAA at given altitudes. During the Middle Holocene , the Earth's magnetic field in the region occupied by the SAA was relatively calm and quiescent, contrasting with its present day activity. The South Atlantic Anomaly seems to be caused by a huge reservoir of very dense rock inside

3264-431: The geomagnetic tail following geomagnetic storms, and are subsequently energized through wave-particle interactions . In the inner belt, particles that originate from the Sun are trapped in the Earth's magnetic field. Particles spiral along the magnetic lines of flux as they move "latitudinally" along those lines. As particles move toward the poles, the magnetic field line density increases, and their "latitudinal" velocity

3332-415: The heart of the trapped radiation belts. In 2011, a study confirmed earlier speculation that the Van Allen belt 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 Anomaly . This suggests

3400-465: The higher parts of the mesosphere) are regions of the atmosphere that are conventionally defined as space. Regions on the Earth 's surface (or in its atmosphere) that are high above mean sea level are referred to as high altitude . High altitude is sometimes defined to begin at 2,400 meters (8,000 ft) above sea level. At high altitude, atmospheric pressure is lower than that at sea level. This

3468-589: The inner Van Allen belt makes its closest approach to the surface at the South Atlantic Anomaly . In March 2014, a pattern resembling "zebra stripes" was observed in the radiation belts by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) onboard Van Allen Probes . The initial theory proposed in 2014 was that—due to the tilt in Earth's magnetic field axis—the planet's rotation generated an oscillating, weak electric field that permeates through

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3536-457: The inner and outer belts may not show the maximum probable flux densities that are possible in the belts. There 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 real time has been limited. The Earth has not experienced a solar storm of Carrington event intensity and duration, while spacecraft with

3604-563: The lapse rate from the dry adiabatic lapse rate to the moist adiabatic lapse rate (5.5 °C per kilometer or 3 °F [1.7 °C] per 1000 feet). As an average, the International Civil Aviation Organization (ICAO) defines an international standard atmosphere (ISA) with a temperature lapse rate of 6.49 °C per kilometer (3.56 °F per 1,000 feet). The actual lapse rate can vary by altitude and by location. Finally, only

3672-907: The letter "A". Athletes also can take advantage of altitude acclimatization to increase their performance. The same changes that help the body cope with high altitude increase performance back at sea level. These changes are the basis of altitude training which forms an integral part of the training of athletes in a number of endurance sports including track and field, distance running, triathlon, cycling and swimming. Decreased oxygen availability and decreased temperature make life at high altitude challenging. Despite these environmental conditions, many species have been successfully adapted at high altitudes . Animals have developed physiological adaptations to enhance oxygen uptake and delivery to tissues which can be used to sustain metabolism. The strategies used by animals to adapt to high altitude depend on their morphology and phylogeny . For example, small mammals face

3740-411: The magnetic field is relatively weak, resulting in a lower repulsion to trapped particles of the radiation belts there, and as a result these particles reach deeper into the upper atmosphere than they otherwise would. The shape of the SAA changes over time. Since its initial discovery in 1958, the southern limits of the SAA have remained roughly constant while a long-term expansion has been measured to

3808-406: The northwest, the north, the northeast, and the east. Additionally, the shape and particle density of the SAA varies on a diurnal basis, with greatest particle density corresponding roughly to local noon. At an altitude of approximately 500 km (310 mi), the SAA spans from −50° to 0° geographic latitude and from −90° to +40° longitude. The highest intensity portion of the SAA drifts to

3876-433: The outer belt). It is thought that proton energies exceeding 50 MeV in the lower belts at lower altitudes are the result of the beta decay of neutrons created by cosmic ray collisions with nuclei of the upper atmosphere. The source of lower energy protons is believed to be proton diffusion, due to changes in the magnetic field during geomagnetic storms. Due to the slight offset of the belts from Earth's geometric center,

3944-472: The proper instruments have been available to observe the event. Radiation levels in the belts would be dangerous to humans if they were exposed for an extended period of time. The Apollo missions minimised hazards for astronauts by sending spacecraft at high speeds through the thinner areas of the upper belts, bypassing inner belts completely, except for the Apollo 14 mission where the spacecraft traveled through

4012-400: The radiation belts will receive about 2,500 rem (25  Sv ) per year. (For comparison, a full-body dose of 5 Sv is deadly.) Almost all radiation will be received while passing the inner belt. The Apollo missions marked the first event where humans traveled through the Van Allen belts, which was one of several radiation hazards known by mission planners. The astronauts had low exposure in

4080-630: The reduction in atmospheric pressure signifies less atmospheric resistance, which generally results in improved athletic performance. For endurance events (races of 5,000 metres or more) the predominant effect is the reduction in oxygen which generally reduces the athlete's performance at high altitude. Sports organizations acknowledge the effects of altitude on performance: the International Association of Athletic Federations (IAAF), for example, marks record performances achieved at an altitude greater than 1,000 metres (3,300 ft) with

4148-409: The reference datum. Pressure altitude divided by 100 feet (30 m) is the flight level , and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions). So when the altimeter reads the country-specific flight level on the standard pressure setting the aircraft is said to be at "Flight level XXX/100" (where XXX

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4216-426: The scientific community. Draining the charged particles from the Van Allen belts would open up new orbits for satellites and make travel safer for astronauts. High Voltage Orbiting Long Tether, or HiVOLT, is a concept proposed by Russian physicist V. V. Danilov and further refined by Robert P. Hoyt and Robert L. Forward for draining and removing the radiation fields of the Van Allen radiation belts that surround

4284-404: 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 adequate shielding if they spend significant time near that zone. Apollo astronauts going through the Van Allen belts received

4352-536: 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 only about 10 micrograms of antiprotons are estimated to exist in the entire belt. The Van Allen Probes mission successfully launched on August 30, 2012. The primary mission was scheduled to last two years with expendables expected to last four. The probes were deactivated in 2019 after running out of fuel and are expected to deorbit during

4420-468: The total electric charge in these circuits is now small enough so as to be comparable with the charge of incoming ions. Electronics on satellites must be hardened against radiation to operate reliably. The Hubble Space Telescope , among other satellites, often has its sensors turned off when passing through regions of intense radiation. A satellite shielded by 3 mm of aluminium in an elliptic orbit (200 by 20,000 miles (320 by 32,190 km)) passing

4488-701: 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 Sun. In the belts, at a given point, the flux of particles of a given energy decreases sharply with energy. At the magnetic equator , electrons of energies exceeding 5000 keV (resp. 5 MeV) have omnidirectional fluxes ranging from 1.2×10 (resp. 3.7×10) up to 9.4×10 (resp. 2×10) particles per square centimeter per second. The proton belts contain protons with kinetic energies ranging from about 100 keV, which can penetrate 0.6 μm of lead , to over 400 MeV, which can penetrate 143 mm of lead. Most published flux values for

4556-425: The west at a speed of about 0.3° per year, and is noticeable in the references listed below. The drift rate of the SAA is very close to the rotation differential between the Earth's core and its surface, estimated to be between 0.3° and 0.5° per year. Current literature suggests that a slow weakening of the geomagnetic field is one of several causes for the changes in the borders of the SAA since its discovery. As

4624-553: The zone of radiation of the Van Allen belts. Beyond the belts, they face 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". 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 vulnerable to radiation, as

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