The degree of anisotropy of cosmic ray electrons of solar origin |
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| Authors: | F R Allum R A R Palmeira U R Rao K G McCracken J R Harries I Palmer |
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| Institution: | (1) The University of Texas at Dallas, Dallas, Texas;(2) Physical Research Laboratory, Ahmedabad, India;(3) University of Adelaide, Adelaide, Australia |
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| Abstract: | Data obtained by the Explorer 34 satellite regarding the degree of anisotropy of ≳ 70 keV electrons of solar origin are reported.
It is shown that the anisotropies are initially field aligned, and that they decay to ≲ 10% in a time of the order of 1 hr.
The decays of the concurrent ionic and electronic anisotropies for one well observed event are in good agreement with the
diffusive propagation model of Fisk and Axford. The data suggest parallel diffusion coefficients for both ions and electrons
that are rigidity independent. From considerations of a long lived electron event, it is shown that the electronic fluxes
exhibit ‘equilibrium’ anositropies at late times. These are interpreted as indicating that convective removal at the solar
wind velocity is the dominant mechanism whereby solar cosmic ray electrons (∼- 70 keV) leave the solar system. They also indicate
that there is a positive density gradient at late times in a solar electron event. The data suggest that this was established
prior to the establishment of a similar gradient for the cosmic ray ions.
This research was supported by the National Aeronautics and Space Administration under contracts NASr-198 and NAS5-9075. The
research in India was supported by funds from the Department of Atomic Energy, Government of India and funds from the grant
NAS-1492 from the National Academy of Sciences, U.S.A. Support in data analysis was also provided by Air Force Cambridge Research
Laboratories, and by the Australian Research Grants Committee. |
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