Magnetospheric Cutoff for 1.5-MeV Extraterrestrial Protons

Fan, C. Y.; Simpson, J. A.; Stone, E. C.

doi:10.1103/physrevlett.12.269

Cited by 7 publications

(1 citation statement)

References 4 publications

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“…During the past few years, high-speed digital computers have been utilized to determine cutoff rigidity values by tracing the orbits of particles through a sixth-degree simulation of the geomagnetic field of internal origin [Shea et al, , 1968Shea and Smart, 1967;$auer, 1963;Kodama, 1965;Kondo and Kodama, 1965;Kodama, 1968]. Although these results appear to be satisfactory for ordering data acquired by cosmic-ray detectors responding to energies greater than 1 Gev, they are unsatisfactory for the high-latitude regions, where particle detectors on balloons, rockets, and satellites have consistently observed energies below the internal field cutoff [Stone, 1964;Webber, 1968;Paulikas et al, 1968]. Ground-based detectors…”

Section: Introductionmentioning

confidence: 99%

The daily variation of trajectory-derived high-latitude cutoff rigidities in a model magnetosphere

Smart¹,

Shea²,

Gall³

1969

J. Geophys. Res.

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Utilizing the trajectory‐tracing procedure, we have calculated the vertical cutoff rigidity at various latitudes along the 260°E meridian for 8 different local times using a model of the magnetosphere represented by a sixth‐degree expansion of the internal field combined with external sources due to currents in the tail and the magnetopause. We find that cutoff rigidities calculated in this magnetospheric model have a pronounced daily variation between the invariant latitudes 60° and 75°, with maximum values near noon and minimum values near midnight. At each local time, vertical cutoff rigidities calculated by means of this model are less than the values found previously by using only internal magnetic‐field sources, and the lowest rigidity particles incident at any local time arrive via the magnetospheric tail. We also find that the daily variation of the proton cutoffs is asymmetric with respect to local noon, the dawn cutoff values being higher than the cutoff values for twilight. This effect is attributed to the longitudinal asymmetry of the magnetosphere. The electron daily variation curve has the inverse asymmetry. Various proton and electron experimental results are found to be consistent with these theoretical calculations.

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Section: Introductionmentioning

confidence: 99%

The daily variation of trajectory-derived high-latitude cutoff rigidities in a model magnetosphere

Smart¹,

Shea²,

Gall³

1969

J. Geophys. Res.

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Theoretical study of cosmic noise absorption due to solar cosmic radiation

Adams¹,

Masley²

1966

Planetary and Space Science

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Local time dependence of non-störmer cutoff for 1.5-Mev protons in quiet geomagnetic field

Stone¹

1964

J. Geophys. Res.

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Two solid‐state detector telescopes, vertically and horizontally oriented, were launched into a polar orbit during a time of low geomagnetic activity. A small flux of 1.5‐Mev protons, interacting with the geomagnetic field as individual particles, was observed at all latitudes above a characteristic cutoff latitude. The observed vertical cutoff was 65° (equivalent dipole latitude) on the night side and 67° on the day side, as compared with a theoretical Störmer cutoff of 76°. The local time dependence was also apparent in the cutoff transition width characterized by the difference in the latitude at which the flux is first detectable and the latitude at which the maximum (plateau) flux is first observed. On the night side, the transition width was about 1°; on the day side it was about 3° and variable. The horizontal cutoff latitudes were similar. Essentially identical results were obtained over north and south poles. These results are not adequately predicted by currently postulated cutoff theories and should be considered in the calculation of proton fluxes associated with polar‐cap absorption.

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Magnetospheric Cutoff for 1.5-MeV Extraterrestrial Protons

Cited by 7 publications

References 4 publications

The daily variation of trajectory-derived high-latitude cutoff rigidities in a model magnetosphere

The daily variation of trajectory-derived high-latitude cutoff rigidities in a model magnetosphere

Theoretical study of cosmic noise absorption due to solar cosmic radiation

Local time dependence of non-störmer cutoff for 1.5-Mev protons in quiet geomagnetic field

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