Solar Wind

Cosmic-ray Modulation by Solar Wind††Phys. Rev. 110,1445-1449 (1958). Section III, on Geocentric modulation, is omitted.*

E.N. PARKER , in Cosmic Rays, 1972

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This chapter focuses on cosmic-ray modulation by solar wind. The hydrodynamic outflow of gas from the Sun as observed by Biermann results in a reduction of the cosmic-ray intensity in the inner solar system during the years of solar activity. The Forbush-type decrease, which is a local geocentric phenomenon, is the result of disordering of the outer geomagnetic field by the outflowing gas from the Sun. It was recently shown that the hydrodynamic flow of gas outward in all directions from the Sun stretches out the magnetic lines of force of the solar magnetic fields, and leads to an essentially radial magnetic field in the inner solar system. The high velocity and low density of this outward streaming gas, the solar wind, leads to anisotropic thermal motions as a consequence of the anisotropic expansion.

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Modern Astrodynamics

COLIN R. MCINNES , MATTHEW P. CARTMELL , in Elsevier Astrodynamics Series, 2006

7.5.1 Geostorm mission

Currently, warnings of geomagnetic storms are made using terrestrial data and real-time solar wind data obtained from the Advanced Composition Explorer (ACE) spacecraft, stationed on a halo orbit [ 28] about the L1 Lagrange point some 1.5 million km (0.01 AU) sunward of the Earth, as shown in Figure 7.8. Since the spacecraft is located sunward of the Earth, coronal mass ejections (CME) sensed by the suite of instruments on-board the ACE spacecraft can be used to provide early warning of impending geomagnetic storms. Typically, a prediction of 30–60 minutes can be made from the L1 point, enhancing the quality of forecasts and alerts to operational user groups. These groups include civil and military satellite operators, electricity utility companies and airlines.

Fig. 7.8. Geostorm mission concept.

To enhance this warning time would require a spacecraft to be stationed at an artificial Lagrange point, sunward of the classical L1 point, as discussed in Section 7.4. While this would require an unrealistic ΔV budget for a conventional spacecraft (of order 9 kms−1 per year of operation), a relatively small solar sail can be used to station a spacecraft approximately 3 million km (0.02 AU) from the Earth, again shown in Figure 7.8. This new artificial Lagrange point will double the warning time of impending geomagnetic storms [5]. The artificial Lagrange point must also be displaced away from the Sun-Earth line so that from the Earth, the spacecraft is viewed away from the solar radio disk to avoid interference with telemetry down-link. The volume of space accessible near L1 in the ecliptic plane is shown in Figure 7.9, along with the Geostorm mission sub-L1 design point. The Geostorm mission makes excellent use of solar sailing by only requiring a modest solar sail characteristic acceleration, but delivering an extremely high effective specific impulse for a multi-year mission duration, as discussed in Section 7.2.3. The solar sail can be transferred to the artificial Lagrange point by chemical kick-stages (and deployed on-station), or the solar sail can perform the transfer.

Fig. 7.9. Volume of space accessible in ecliptic plane for sail loadings 20–35 gm−2.

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Atomic Data Needs for Understanding X-ray Astrophysical Plasmas

Randall K. Smith , Nancy S. Brickhouse , in Advances In Atomic, Molecular, and Optical Physics, 2014

2.3 Charge Exchange

Although charge exchange can and does create detectable X-ray emission, e.g., in solar wind interactions with comets ( Cravens, 1997), it impacts the ionization balance of X-ray emitting plasmas only in primarily neutral regions where high-energy photons or cosmic rays create inner shell vacancies (Greenwood et al., 2004). Kingdon and Ferland (1999) considered the effects of charge exchange on the ionization balance of a photoionized plasma, using the CLOUDY model as a test bed. They discovered that the charge exchange reactions typically heat the plasma but that the overall impact is localized to a narrow transition zone where hydrogen becomes ionized. Furthermore, they found the most important transitions are from ions with primarily optical and UV transitions, such as C+   3 and O+   2, rather than for ions that emit primarily in the X-ray band. Seon (2004) considered this issue for collisional plasmas at temperatures below 8 × 104  K, but to our knowledge the impact of charge exchange on X-ray-emitting astrophysical collisional plasmas has not been considered.

Fusion researchers have studied this process in detail as charge exchange at high velocity (neutral beam heating) can be used to add energy to a magnetically confined plasma via the injection of high-energy neutrals (see Isler (1994) for a review). These high energy neutral hydrogen atoms are injected with E  >   10   keV, much more energetic than typically found in astrophysical sources. However, charge exchange at lower energies can occur within the confined plasma when an impurity ion interacts with thermal hydrogen atom (e.g., Isler and Crume, 1978). This interaction will affect the relative ionization state of these ions, but more of ten is used as a ion temperature and velocity diagnostic (Isler, 1994) and so will be discussed in Section 3.6 below.

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ELECTROMAGNETISM

Jerry B. Marion , in Study Guide for Physics in the Modern World (Second Edition), 1981

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This chapter describes the properties of magnets, the general characteristics of the earth's magnetic field, and the effect of the solar wind upon it. An electric current produces a magnetic field, and there is the right-hand rule for determining the direction of the magnetic field lines surrounding a current-carrying wire. Magnetic field lines are always closed; they have neither beginning nor end. An electric charge experiences a force in a magnetic field only if it is in motion. The chapter explains the working of electric meters and galvanometer. The basic idea of electromagnetic induction is that when a conductor and a magnetic field are in relative motion, a current is induced to flow in the conductor. According to Lenz's law, an induced current produces an effect that opposes the change that produced it.

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Environmental Damage to Electronic Products

Milton Ohring , in Reliability and Failure of Electronic Materials and Devices, 1998

Answer

In 1 cm3 of A12O3 there are 1 × 10−6 × 1 cm3 × 3.9 g/cm3 = 3.9 × 10−6 g of U238. This corresponds to 6.85 × 10−7 Ci/g × 3.9 × 10−6 g/cm3 = 2.67 × 10−12 Ci/cm3, or an equivalent radiation flux of 2.67 × 10−12 Ci/cm3 × 14 × 10−4 cm = 3.74 × 10−15 Ci/cm2. Collecting terms, 8 α P /dis × 0.25 × (3.74 × 10−15 Ci/cm2) × (2.2 × 1012 dpm/Ci) ×60 min/h = 0.98 αP/cm2-h.

Typical αP flux levels in IC chips without tungsten silicides rarely exceed 0.005 αP/cm2-h. Ceramic packaging components (lids, leadframes) may exhibit flux levels ten to as much as a thousand times larger. In both cases there is considerable scatter, depending on processing conditions and involved vendors. Nevertheless, such αP fluxes are sufficient to cause troublesome SEUs. Details of the αR damage mechanism and energy required in silicon will be treated in Section 7.6.6.4.

An interesting example of chip contamination by such radioactive elements involves Po210, an isotope of polonium that occurs naturally as a daughter of radon gas. Hera RAM memory chips manufactured by IBM in 1987 were found to be contaminated by Po210, an alpha emitter, such that hot chips suffered failure rates a thousand times higher than clean chips. Following a frantic search for the source of contamination, the culprit was found to be radioactive nitric-acid bottles. In producing these, the manufacturer had to meet stringent semiconductor standards of cleanliness. Therefore, a bottle-cleaning machine employing radioactive Po210 was used (as in smoke alarms) to ionize an air jet that dislodged electrostatic dust left behind after washing. The jets leaked radioactivity only intermittently, confounding the problem. This example is illustrative of the painstaking efforts that periodically surface in the industry to track down and eliminate sources of SEUs.

b.

Nuclear particles from cosmic rays The second, and in many ways more troubling, source of nuclear particles stems from cosmic rays that bombard Earth from the recesses of outer space. Primary sources of cosmic rays are energetic galactic particles and solar-wind particles. The former are far more energetic than the latter, which typically have energies of ∼1 GeV. Secondary cosmic rays are generated when the primary cosmic rays hit atmospheric atoms and create a shower, or cascade, of secondary particles. Finally, there are the terrestrial cosmic rays that hit Earth. These are composed of assorted nuclear particles, e.g., neutrons, pions, protons, and muons, that have energies ranging from 1 MeV to 1 GeV. About 97% of the nucleon flux at sea level is due to neutrons, and fluxes are typically 105/cm2-yr. It is interesting to note that cosmic-ray fluxes vary strongly with solar cycle activity and altitude (45). In going from New York (0 ft) to Denver (5280 ft) the neutron flux increases 3.4 fold, and at Leadville, Colorado (10,200 ft), the flux is 12.8 times higher than at sea level. This trend continues and accounts for the fact that the soft fail rate of electronics at airplane altitudes is 100 times the magnitude recorded at terrestrial altitudes.

A relative comparison of the radioactive and cosmic-ray contributions to soft error rates (SER) depends on various factors, including levels of nuclear conta mination, location, and altitude of devices. Data for Po210 contaminated 288 Kb DRAM chips in Fig. 7-13 depicts measured soft error rates as a function of time and altitude. The results can be described by the equation

Fig. 7-13. Soft error rates for 288 Kb DRAMs contaminated with Po210 measured at various altitudes. The solid line is the alpha-particle component of SER, while the vertical distance above (dotted lines) corresponds to the cosmic ray contribution to the SER.

 From T. J. O'Gorman, J. M. Ross, A. H. Taber, J. F. Ziegler, H. P. Muhlfeld, C. J. Montrose, H. W. Curtis, and J. L. Walsh, IBM J. Res. Develop. 40 (1), 41 (1996). Copyright © 1996

(7-43) SER = A exp ( - t τ 1 / 2 ) + B + C ,

where A is the initial SER due to Po210 contamination, τ1/2= 138 d half-life, B is the contribution due to longer-lived alpha emitters, and C is the cosmic ray contribution.

The roles of these radiation sources may also be coupled. For example, cosmic-ray activation of boron in borophosphosilicate glass has recently been suggested as a dominant source of alpha particles that cause soft errors in Si (46).

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Theoretical, Experimental, and Numerical Techniques

MICHAEL GEDALIN , in Handbook of Shock Waves, 2001

3.6.1 INTRODUCTION

Gasdynamic shocks form each time a high velocity supersonic flow is stopped by an obstacle. One of the most important distinctions between space shocks and ordinary shocks in gases is that the medium space shocks form in is a plasma-ionized gas. Another very significant property of these shocks is that the plasma almost always is embedded in an ambient magnetic field, which is compressed by the shock. Therefore, these shocks form whenever the plasma flow velocity exceeds the corresponding signal velocity in the magnetized plasma (de Hoffman and Teller, 1950; Tidman and Krall 1971).

Shocks are ubiquitous phenomena in space. Many different kinds of shocks have been observed in the solar system. Planetary bow shocks (Russell, 1985 ) are formed when the solar wind encounters a planetary magnetosphere, whether natural (as on Earth, Jupiter, and Saturn, which have their own magnetic field) or induced (as on Mars and Venus). Cometary shocks are produced by the interaction of the solar wind with charged particles of cometary origin. Interplanetary shocks appear whenever fast solar wind overtakes slow wind. Since the solar wind is super-magnetosonic, and the solar system velocity relative to the interstellar plasma is also super-magnetosonic, both the solar wind and interstellar flows should be decelerated to subsonic velocities at the heliopause that separates the two plasmas. This is achieved at the termination shock and heliospheric bow shock, respectively, which are formed on both sides of the heliopause. Shocks, believed to be produced by supernova explosions, play an important role in cosmic ray generation, that is, acceleration of charged particles to high energies.

Another feature of these shocks that distinguishes them from gasdynamic shocks is that the mean free path for Coulomb collisions in the system is much larger than the system size itself. For example, at the Earth orbit the electron Coulomb mean free path is larger than the distance to the Sun. This means that these shocks are essentially collisionless. As a result, the shock features (scales, particle energization, and dissipation) are quite different from those of shocks where collisions are substantial.

In this chapter we will discuss the modern theory of these shocks and observations. In Section 3.6.2 we present the magnetohydrodynamic (MHD) description of the shock transition. In Section 3.6.3 we briefly discuss shock classification. Section 3.6.4 is devoted to in situ observations of the Earth bow shock. Theoretical developments related to the shock structure and particle motion in the shock front are discussed in Section 3.6.5. Shock particle acceleration is described in Section 3.6.6. For the reader's convenience throughout we prefer to cite more recent books and review papers, which contain a number of further references, rather than priority papers.

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Cosmochemical Applications Using Mass Spectrometry

J.R. De Laeter , in Encyclopedia of Spectroscopy and Spectrometry, 1999

Planetary science

Mass spectrometry is ideally suited to the investigation of planetary atmospheres and cometary material in terms of both elemental and isotopic abundances. Mass spectrometers have been an integral component of space probe instrumentation because they are mechanically robust, have a low power consumption, yet are sensitive and versatile.

Dust particle impact mass spectrometers were carried on space probes that approached close to Halley's comet in 1986. These are time-of-flight mass spectrometers of the design shown in Figure 10 . The data confirm that the dust from the comet is essentially solar in both elemental and isotopic composition. A double focussing mass spectrometer was also used to determine the composition, density and velocity of the neutral gases and of low-energy cometary ions. This mass spectrometer showed that the neutral gas composition of the coma of Halley's comet was dominated by water vapour and other light element constituents. The third mass spectrometer carried on the Halley space probes was designed to determine the composition, density, energy and angular distribution of ions in the solar wind and cometary plasma. This ion mass spectrometer consists of two independent sensors – a high-energy range spectrometer and a high-intensity spectrometer. As the space probe Giotto approached comet Halley, H +, C+, H2O+, CO+ and S+ were found in a diffuse shell-like distribution out to 3 × 105 km from the comet. As Giotto penetrated the atmosphere to within 1300 km to the nucleus of the comet, the main ion species were H+, H2 +, C+, OH+, H2O+, H3O+, CO+ and S+. The gas and dust stream emitted from comet Halley contains a higher proportion of volatiles than is found in meteorites, which is consistent with the comet's original location in the cooler regions of the Solar System. Isotopic measurements show that O, S, C, Mg, Si and Fe in cometary and stratospheric dust particles are typical of those found in other Solar System material, implying that the dust has the same nucleosynthetic reservoir as the rest of the Solar System. On the other hand, isotopic anomalies in H and Mg confirm meteoritic evidence that some solid particles survived the homogenization processes that occurred in the early history of the Solar System.

Figure 10. Schematic diagram of the time-of-flight dust-particle impact mass spectrometer which was mounted in a space probe to examine the mass spectra of dust particles from Halley's comet.

The particle flux that is part of the expanding corona of the Sun is known as the solar wind. The elemental and isotopic composition of the solar wind was studied by various space craft in the period 1965–1975, all of which carried electrostatic positive ion analysers. An ideal opportunity for further study was afforded by the Apollo mission to the Moon, in that aluminium foil collectors were exposed on the lunar surface in the Apollo 11–16 missions which were then analysed for the noble gases by gas source mass spectrometry on the returned Al foil.

The lunar soil is an ideal repository for implanted solar wind elements, as are certain gas-rich meteorites. Deuterium is depleted relative to the terrestrial standard in these materials, the D:H ratio of < 3 × 10−6 being consistent with the hypothesis that D is converted into 3He in the proto-Sun. Ion probe mass spectrometry has been used to study Mg, P, Ti, Cr and Fe which are present to enhanced levels in lunar minerals, indicating an exposure age of approximately 6 × 104 y. The isotopic data indicate that the light isotopes of a number of elements have been preferentially lost from lunar material because of volatilization by micrometeorites or solar wind bombardment. There is some indication, from a study of Ne in gas-rich meteorites, of a large solar flare irradiation during the early history of the Solar System, perhaps related to the T-Tauri phase of the Sun.

Isotopic studies of Gd, Sm and Cd from lunar samples show depletions in those isotopes which possess large thermal neutron capture cross sections. This has not only enabled the integrated neutron flux and neutron energy spectrum in the lunar samples to be determined, but has provided information on the stability of the lunar surface by analysing these elements and the noble gases in lunar core material.

Interplanetary dust particles (IDPs) can be collected on adhesive surfaces by U-2 aircraft at altitudes of 20 km, and a fraction of these have been identified as of non-terrestrial origin. Some of these IDPs have been analysed by gas source mass spectrometry using a double focussing instrument employing the Mattauch–Herzog geometry (Figure 11). The measured 3He:4He and 20Ne:22Ne ratios are lower than those observed in the solar wind. The sensitivity of static gas source mass spectrometry is such that stepwise heating of these IDPs has the potential to elucidate the thermal history of the stratospheric particles, which enables cometary and asteroidal origins to be differentiated.

Figure 11. Schematic diagram of the high-performance, double focussing mass spectrometer used to measure the isotopic composition of the noble gases on IDPs.

Mass spectrometers were an integral component in the scientific payload of Viking Landers 1 and 2 and were designed to measure the composition and structure of Mars' upper atmosphere. Carbon dioxide is the major constituent of the atmosphere, whilst the isotopic composition of C and O in the Martian atmosphere is similar to that of the terrestrial atmosphere. However, 15N is enriched in Mars' atmosphere by approximately a factor of 1.6. Certain meteorites have been identified as samples from the Martian crust. These SNC meteorites, including the orthopyroxenite ALH84001, on which claims for the evidence of life on Mars have been based, have produced a large quantity of isotopic evidence which has been used in conjunction with the Viking Lander data. Since meteorites are delivered to our doorstep, free of charge as it were, it is important to acquire and classify new samples because of their potential value to planetary science.

Meteorites have provided the bulk of the data on which the 'cosmic' abundance distribution has been established, which led directly to the canonical theory of nucleosynthesis. A range of nucleosynthetic sites is now available for laboratory study and nucleosynthetic models can be compared with measured isotopic compositions. Isotopic data on refractory inclusions and prestellar grains from primitive meteorites are a new source of astrophysical data, giving fresh insights into nuclear processes in stars. Isotope abundance measurements have also been invaluable in giving a cosmochronological time scale to the major events in the history of the universe. Mass spectrometers have been an essential component of the payload of space probes to the planets and Halley's comet, and technological advances have even enabled the noble gases in IDPs to be measured isotopically.

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Photocatalysis: Fundamental Processes and Applications

Umesh A. Fegade , Ganesh N. Jethave , in Interface Science and Technology, 2021

15.1.1.1.2 Improved public health

Water and air pollution emitted by coal and from natural gas plants are related to respiratory problems, heart attack, neurological damage, premature death, cancer, and other serious problems. Most of these natural health effects are not produced by clean energy technology, which comes from air and water pollution. Wind, solar, and hydroelectric systems generating electricity do not produce air pollution. Some atmospheric contaminants are removed from biomass and geothermal systems, while emissions of gas are much smaller than coal and gas plants. Furthermore, water and sunshine need no required water, and therefore, through comparison with irrigation, drinking water, or other essential water requirements, do not contaminate water or tension supplies. Fossil fuels, on the other hand, have big implications on supplies of water: both coal and gas drilling can contaminate the source of potable water, and water is used to power coal, gas, and oil thermal generation plants. Geothermal power projects like biomass and coal may need water to cool down. Hydroelectric power plants can obstruct the flow of a river on both sides [4, 8].

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Cosmic Radiation

Michael F. L'Annunziata , in Radioactivity (Second Edition), 2016

14.5 Origins of Cosmic Radiation

The origins of galactic and extragalactic cosmic rays remains an unsolved problem, and reviews on this subject matter are provided by Potgieter (2010), Blasi (2008), Hörandel (2008b), and Gaisser (2001).

In brief, cosmic rays can originate from (1) energetic particles associated with mass ejections from solar flares and similar energetic solar events; (2) anomalous cosmic rays, which are particles of interstellar origin accelerated at the edge of the heliopause and accelerated at the termination shock in the solar wind; (3) high-energy particles of galactic origin far outside the heliosphere or our solar system; and (4) extragalactic sources, which give rise to particles of the highest energies of ∼10 18  eV or higher.

The sun has been identified as one of the sources of high-energy cosmic-ray particles that hit the top of the atmosphere, and these particles can be accelerated during solar flares. The mass ejections associated with solar flares drive shocks into the interplanetary medium, where particles undergo acceleration via shocks in the heliosphere. Linked to these are the anomalous cosmic rays, which are classified as a subset of particles accelerated in the heliosphere; these are particles of interstellar origin accelerated at the termination shock in the solar wind (Gaisser, 2000). Neutron monitors are used to detect the secondary neutrons produced by the cosmic-ray nucleon collisions with nuclides of the earth's atmospheric molecules. The gamma-ray images of the galaxy taken in space provide evidence for the gamma radiation produced by interactions of the accelerated particles in the solar atmosphere in addition to gamma radiation originating from neutral meson decay described previously.

Galactic cosmic rays can arise from a supernova, which is the final stage in a star's evolution. During the death of a star, it explodes as a supernova, producing heavy particles and accelerating them in a shock wave into interstellar gas. Supernovae are sources of galactic cosmic rays, with particles undergoing acceleration to ∼1015  eV or higher. The interactions of these accelerating particles also serve as sources of gamma radiation that we detect throughout the galaxy.

Accelerated particles in excess of approximately 1018  eV or higher are considered to be possibly of extragalactic origin. Most galactic cosmic rays are confined by the magnetic field lines of the galaxy. Extragalactic cosmic-ray particles with sufficient energy to invade our galaxy (1018 to beyond 1020  eV) are relatively few in number, as discussed previously. Several theories and models exist for the origins of extragalactic cosmic rays and these are reviewed by Gaisser (2000).

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Local Peculiarities

A.M. HILLAS , in Cosmic Rays, 1972

8.3 The Earth's magnetosphere

Recent work has shown that the simple picture of the motion of charged particles in the geomagnetic field given in Chapter II is incomplete: there are other local cosmic ray effects associated with the magnetosphere which deserve a mention.

(i)

The Earth's dipole field has a sharp boundary where it gives way to the interplanetary field. Pressure from the plasma of the solar wind deforms it so that some lines of force are blown out as a long tail behind the Earth, and on the sunward side the regular geomagnetic field ends sharply at about 10 Earth radii, at the magnetopause: beyond this lies a disturbed region where the solar plasma flows round the magnetosphere from which it is largely excluded; and near 14 Earth radii lies a magnetohydrodynamic collisionless shock wave marking the boundary of the steady solar wind. Figure 29 shows the field configuration constructed from numerous Russian and American satellite observations. At high magnetic latitudes ( > ˜ 60 ˆ ) the cut-off rigidity varies from day to night, e.g. from ∼ 160 MV to ∼ 15 MV at Churchill.

FIG. 29. Comet-like deformation of the outer magnetosphere. Shading marks areas of trapped radiation.
(ii)

The presence of local and temporary islands of electrons of tens ofkeV—well downstream in the tail, near the magnetosphere boundaries, and precipitating in the auroral zones—shows that processes of particle acceleration take place in the magnetosphere, particularly in geomagneticaliy disturbed conditions. Theoretical work suggests also that there may be an electric field capable of accelerating electrons and protons by many tens of keV along the magnetic neutral plane which is found in the equatorial region of the tail. Hence one may have here another laboratory for studying particle acceleration by plasmas.

(iii)

Belts of trapped radiation in the magnetosphere fill orbits which Størmer's theory (Chapter II) shows to be inaccessible to particles approaching from outside, and from which particles conversely cannot escape—for instance, from the inner allowed zone in Figure 4c on p. 18. The characteristic orbit is one in which a particle spirals around a line of the dipole field, with the pitch angle of the helix increasing as it approaches the Earth, sin2 ϑ / B remaining constant until when ϑ = π / 2 the particle turns back and spirals to another mirror point in the opposite hemisphere. A drift around the Earth is superimposed on this to-and-fro motion. In Figure 7 (p. 22), the particle of lowest rigidity is in a nearly-trapped orbit. In 1962, a high-altitude hydrogen bomb explosion—"Starfish"—injected so many relativistic electrons into the lower trapping region that the natural electron flux here has become obscured; and from this it is clear that at some altitudes the particles can remain in trapped orbits for years.

The flux is very high, exceeding 108 particles cm−2 s−1, and completely stopped Van Allen's counters when it was first encountered in 1958; though the most numerous particles are of low penetrating power. Both electrons, of energies between a few keV and a few MeV, and protons from 100 keV to 100 MeV have been detected, with the more energetic particles trapped closer to the Earth, and the less energetic electrons extending to about 8 Earth radii. Most of the energy is in the low-energy protons.

Some of the inner-belt particles are injected by the decay of neutrons ejected from cosmic-ray interactions in the atmosphere, but the variability of the outer regions, and to a lesser extent the inner zone, requires a more rapid source of replenishment, and it appears that thermal protons from the solar plasma must be caught up in the varying outer fields and somehow gradually driven further in, increasing their energy as they pass into the stronger fields.

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