Radiation measurements to 1500 kilometers altitude at equatorial latitudes

Holly, Francis E.; Allen, L.S.; Johnson, R. G.

doi:10.1029/jz066i006p01627

Cited by 27 publications

(6 citation statements)

References 10 publications

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“…Flux ($) modulation has been provided by both a magnetic field 1 and separately by a vector potential alone 4 ; mechanical momentum modulation was provided indirectly by a current flow. 2 In the experiment reported here the flux is held constant and the mechanical momentum provided directly by an actual rotation (Q) of the circular interferometer (Z=mr 2 £2). In terms of this rotation the maximum supercurrent through the interferometer is…”

Section: Cos27r (H*)|>mentioning

confidence: 99%

Observation of Nearly Monoenergetic High-Energy Electrons in the Inner Radiation Belt

Imhof

Smith

1965

Phys. Rev. Lett.

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Previous measurements 1 " 5 have given a rather incomplete picture of natural inner-belt electron spectra, but the energy distributions are thought to be generally monotonic and rather smooth. The purpose of this brief paper is to present some sharply peaked electron spectra observed in the inner belt. The data were acquired during the period 30 October to 4 November 1963, shortly after a major magnetic storm, in the narrow spatial interval where Mcllwain's L parameter 6 varies from 1.14 to 1.17, corresponding to a region where the high-energy electrons from Starfish had long since decayed. The electrons observed at -1.3 MeV decayed at a rate in reasonable agreement with that calculated from atmospheric scattering theory, both with respect to absolute value and variation with L.The measurements were performed from an earth-oriented satellite in polar orbit with 355km apogee and 288-km perigee. The spectrometer was designed for high sensitivity and an acceptance solid angle of nearly 2ir sr. It consisted of a 5.7-cm-diameter by 3.2-cm plastic scintillator shielded on the sides and back by at least 3.4 g/cra 2 of aluminum and light pipe, and on the front earthward-facing surface by a 0.33-cm tungsten sheet with a 2.54-cm-diameter entrance aperture. Data were recorded with a differential 16-channel pulse-height analyzer of the digital time-converter type oper-ating in two energy ranges of 0.3 to 2.6 MeV and 0.3 to 10.0 MeV, thus providing resolution consistent with that of the detector, continuous energy coverage, and laboratory-like channel linearity and stability, all necessary for the type of measurements reported here. Individual counts were stored as four-bit words in an on-board tape recorder, giving complete orbital coverage. The spectra observed throughout most of the radiation belts were rather smooth and monotonic and have been reported elsewhere. 7 " 9On very low-L shells, however, we consistently observed rather sharply peaked spectra. Reprocessing the previously analyzed 9 data in much shorter intervals revealed a systematic and rapid variation of spectrum with L. Figure 1 shows the raw spectra observed during one of the many passes through this narrow J5, L interval. At L = 1.150 the peak is not much wider than our instrumental energy resolution of-18% at 1.3 MeV.Laboratory tests have shown that gamma rays or neutrons cannot produce such a narrow peak, nor can even monoenergetic protons in any pancake angular distribution because of varying energy loss with angle in the 0.025-cm polyethylene entrance foil. From many preflight calibrations and all of the in-flight data, we conclude that this peak could not have been caused by an electronic malfunction. For example, 885

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Section: Cos27r (H*)|>mentioning

confidence: 99%

Observation of Nearly Monoenergetic High-Energy Electrons in the Inner Radiation Belt

Imhof

Smith

1965

Phys. Rev. Lett.

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“…The counter data of Holly [1960] indicate that the ma'ximum counting rate for protons of energy greater than 52 Mev occurred at 8øN, 45øW, at an altitude of 1100 km--after the nose cone reached apogee. On the basis of the Holly [1960] data, it is calculated that if all the counts had been recorded at the peak counting rate, they would have come in a period of about 360 seconds. This is the time interval we have used in our calculation of the flux at 1100-km altitude.…”

mentioning

confidence: 95%

“…The nose cone was separated from the vehicle before entering the radiation belt, and it reached a maximum altitude of 1125 km. The approximate traiectory is shown in Figure 1, which gives the flight path of a pod that was released from the missile after launching [Holly, 1960]. The nose cone and pod are believed to have been within a few kilometers of each other throughout the flight.…”

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confidence: 99%

Charged particles in the inner Van Allen radiation belt

Armstrong¹,

Harrison²,

Heckman³

et al. 1961

J. Geophys. Res.

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A nuclear emulsion stack was flown through the lower part of the inner Van Allen radiation belt a few days after the intense solar flares of July 10–16, 1959. The stack ‘looked out’ through a thin window on the mounting plate at the rear of the nose cone. Protons with incident energies down to 42 Mev were recorded. The total proton flux is about ⅓ that reported by Freden and White; the difference may be due to the lower peak altitude of the flight reported here. Above 100 Mev the proton spectrum is consistent with the neutron albedo hypothesis. Below 100 Mev, however, there is evidence of structure, with a peak or plateau in the region of 80 Mev. This structure may be due to solar protons.

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“…also been measured by Holly et al [1961] with Geiger counters aboard various Atlas pods, but no systematic spacial dependence was reported.…”

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confidence: 99%

Proton intensities and energy spectrums in the inner Van Allen belt

Imhof¹,

Smith²

1964

J. Geophys. Res.

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Proton intensities and energy spectrums in the inner Van Allen belt have been measured with shielded plastic scintillators on three satellites and an Atlas pod. Omnidirectional fluxes of protons above 59, 95, and 148 Mev are given at the equator for L values of 1.25 and 1.48-1.60, and isofiux contours are given in B, L space for protons above 59 Mev. The counting rates of three scintillation counters having threshold energies of 46, 76, and 128 Mev have been analyzed in terms of assumed energy spectrums of the form d•/dE --AE -'• and d•/dE --Ae -•/•o. The second form produces a dependence on the geomagnetic parameter L given by E0 --460L -4-8 Mev. For the theoretical spectral shapes of Lenchek and Singer, cutoff energies have been derived from the ratios of counting rates in the three detectors. The results are in moderately good agreement with the calculations of Singer (in which, because of nonadiabatic effects, the cutoff momentum was found to be of the form Pmax •-PoL-•), with a best fit value P0 --2000 Mev/c. Introduction. Since the experimental verification by Freden and White [1959] of the existence of protons in the inner Van Allen belt, considerable theoretical and experimental effort has been devoted to understanding the spacial and energy variations of the proton flux. Theoretical calculations have been devoted to both injection mechanisms [Singer, 1958, 1960; Hess, 1959; Kellogg, 1959; Vernov et al., 1959; Ray, 1960] and various loss mechanisms, involving both quiescent nonadiabatic effects [Singer, 1959] and the possible existence of hydromagnetic waves [Dragt, 1961; Wentzel, 1961]. Proton energy spectrums have been measured with emulsions by Freden and White [1959], Armstrong et al. [1961], Heckman and Armstrong [1962], and Naugle and Kniffen [1961]. These experiments provide excellent measurements of energy spectrums, but with one exception [Naugle and Kniffen, 1961] they do not provide information on variations of the spectrum with position in space. Spacial variations of the proton flux have been obtained with counters placed on various satellites, but most of these measurements have not been accompanied by the detailed spectral measurements necessary for a complete understanding of the phenomena involved. With two Geiger counters aboard the satellite Explorer 4, Mcoe1wain and Pizzella [1963] have studied variations of the energy spectrum with position in space for protons in the range of 30 to 40 Mev. A wide range of energy spectrums have

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Radiation measurements to 1500 kilometers altitude at equatorial latitudes

Cited by 27 publications

References 10 publications

Observation of Nearly Monoenergetic High-Energy Electrons in the Inner Radiation Belt

Observation of Nearly Monoenergetic High-Energy Electrons in the Inner Radiation Belt

Charged particles in the inner Van Allen radiation belt

Proton intensities and energy spectrums in the inner Van Allen belt

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