The radiation belt produced by neutrons leaking out of the atmosphere of the Earth

Hess, W. N.

doi:10.1029/jz065i010p03107

Cited by 18 publications

(14 citation statements)

References 19 publications

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“…The beta decay electrons from neutrons certainly contribute to the outer belt [Hess, 1960;Dessler and Karplus, 1960]. Recently, however, it was shown that processes other than injection of neutron decay electrons must be operative in order to account for the spatial distribution of electrons in the outer belt [Hess, Killeen, Fan, Meyer, and Simpson, 1961].…”

Section: Parameters For Electron Flux and Energy Density Inmentioning

confidence: 99%

Dynamics and structure of the outer radiation belt

Fan¹,

Meyer²,

Simpson³

1961

J. Geophys. Res.

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From an analysis of electron measurements in the Explorer VI satellite (August 7–October 6, 1959) four time‐dependent parameters which characterize the outer electron belt have been investigated. They are: (1) the equatorial electron intensity I0; (2) the equatorial range from the earth R0 of the peak intensity; (3) the electron‐density distribution along a line of force through the intensity peak; and (4) a measure of the change in electron spectrum with time. These parameters, along with measurements of magnetic field intensity, make it possible to study the origin of the changes in electron intensity and distribution which are known to occur in the outer belt. Several magnetic storms occurred during the observation on Explorer VI. Within the sequence of changes in the outer belt induced by these geomagnetic storms, there are some changes of the parameters which are accounted for only by invoking an irreversible energy gain or loss within the outer belt. The energy gain process appears to be through irreversible local acceleration of electrons. The energy loss process leads to a stable mirror‐point distribution characteristic of the periods between geomagnetic storms. The time intervals within which each of these processes is operative are identified. Reversible processes are possibly the cause for other changes. The foregoing analysis rests upon the proof given in this paper that the outer‐belt peak intensity coincides over a wide range of geomagnetic latitudes with magnetic field lines of force in the centered dipole approximation. Consequently, the measured electron‐intensity maximum is used as a ‘tracer’ of the geomagnetic field lines of force for analyzing changes in the outer belt with time. It is shown that even during geomagnetic storms the trace of the electron‐intensity maximum followed a centered dipole line of force. This indicates that at all times the particle‐energy density of the radiation belt is much less than the energy density of the magnetic field in the region. The electron fluxes, high‐energy proton fluxes, and possible electron spectra are investigated. Two distinct peaks of electron intensity are identified to persist in the outer belt for about 2 months, and it is shown that these peak distributions undergo radial motion during geomagnetic disturbances.

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Section: Parameters For Electron Flux and Energy Density Inmentioning

confidence: 99%

Dynamics and structure of the outer radiation belt

Fan¹,

Meyer²,

Simpson³

1961

J. Geophys. Res.

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“…Vew little is known about the source of the radiation, although three general origins have been discussed. They are, first, the injection of electrons into the trapping region from the decay of cosmic-ray albedo neutrons [Hess, 1960]; second, the direct injection of electrons into the trapping region from solar gas clouds; and last, the local acceleration of low-energy electrons present in the exosphere or from the solar stream [Van Allen and F•'a•k, 1959b; A•'noldy, Ho#man, and Winckle•', 1960b]. It is possible that all the above-mentioned sources, and perhaps even some that have not been considered, contribute to the intensity of the radiation.…”

Section: Because the Prop/gm And Scint/gm Ratio Curves Rise When Fiatmentioning

confidence: 99%

Observation of the Van Allen Radiation Regions during August and September, 1959: 4. The outer-zone electrons

Arnoldy¹,

Hoffman²,

Winckler³

1962

J. Geophys. Res.

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A study is reported of the data from the radiation detectors abroad the Explorer VI earth satellite (1959δ1, launched August 7, 1959) as the spacecraft passed through the outer zone during a period when the count rate time variations and the geomagnetic activity were low. The radiation detectors aboard the satellite were an ionization chamber, a Geiger counter, a proportional counter telescope, and a scintillator. Extensive calibrations were made to determine the response of these detectors to monoenergetic electrons when inside a spare payload. In using these calibrations and fitting assumed power‐law spectra of electrons to the data, it is seen that the spectrum is flat and must extend to several Mev at the small ranges, with the ion chamber and Geiger counter responses there due primarily to direct electron detection. The intensity of the energetic electrons is shown to decrease with increasing range as the spectra steepen and the radiation softens, resulting in an increasing contribution of bremsstrahlung to the rates of the chamber and Geiger counter. Any attempt to utilize the bremsstrahlung response of the Explorer VI detectors to determine fluxes is useless if an appreciable portion of their counting rate is produced by direct energetic particles. The spectral shape of the outer zone as suggested by this analysis allows us to interpret the minimum observed in the Geiger counter rate at an equatorial geocentric range of 19,000 km as having spectral‐detector origin rather than as representing the removal of radiation by an anomaly in the earth's magnetic field. This analysis is only capable of fitting trial spectra to the data; the procedure does not eliminate the possibility of more complex spectra existing in the outer zone which would lead to different conclusions about the nature of the trapped radiation.

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“…and Hess [1960] have proposed that the relative minimum in the outer belt as measured by radiation detectors aboard Explorer VI earth satellite is caused by a predominantly low-altitude injection from neutron albedo decays and a local loss of particles when those with low mirror points drift through the Capetown magnetic anomaly. To the contrary, this note will show, assuming the validity of present magnetic data, that any particles affected by the Capetown anomaly do not have trajectories that would pass through the position of the observed minimum in the outer belt.…”

Section: Dessler and Karplusmentioning

confidence: 99%

“…The effect of the Capetown magnetic anomaly on the motion of trapped particles has been thoroughly discussed by Dessler [1959] and Dessler and Karplus [1960], and therefore will not be repeated here. Hess [1960] and Hess and Killeen [1960] have calculated that the depth of the gap as it would be seen by radiation detectors, assuming a neutron source injection, to be The particles that would have mirror points below about 1300 km over the anomaly are of interest because at this altitude they begin to be rapidly scattered into the atmosphere. The locus of the mirror points of these particles must be followed as they drift in longitude around the earth to 148øE longitude.…”

Section: B Capetown Magnetic Anomaly and Particle Trajectoriesmentioning

confidence: 99%

“…Therefore it is not likely that agreement can be reached between the actual l•osition of the minimum and the equatorial range of the trajectories through the anomaly. Dessler and Karplus [1960] and Hess [1960] have also used the theory of the anomaly causing the minimum as supporting evidence for the neutron albedo decay source of the outer belt. In order to cause the minimum in the equilibrium population of the particles, the local decrease in magnetic field strength at the anomaly would require an injection of particles that is strongly weighted toward the surface of the earth.…”

Section: D•scuss•onmentioning

confidence: 99%

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