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Electron injection and acceleration at nonlinear shocks: Results of numerical simulationsWe present results of numerical simulations of electron injection and acceleration at nonlinear high Mach number shocks. The electrons are assumed to be heated at the thermal subshock to an energy E(sub inj), which is treated as a free parameter, above which they are injected by self-generated whistlers to momentum m(sub p) x V(sub A). This injection mechanism requires Mach numbers greater than (43/(beta(sub -)))(((k T(sub e))/(E(sub inj)))(exp 1/2)), where T(sub e) and beta (sub -) are the upstream electron temperature and plasma beta parameter. Above m(sub p) x V(sub A) electrons are trapped in the shock by Alfven waves. In the proton precursor region the Alfven waves are assumed to be generated by protons accelerated at the shock, and have nonlinear intensities. Below GeV, however, electrons of a given rigidity propagate faster than protons with a similar rigidity and therefore diffuse to regions ahead of the proton precursor. In those regions the Alfven waves are generated by the electrons themselves. The diffusion coefficient appears to increase with decreasing acceleration efficiency. As a result, the number of electrons accelerated to energies GeV and above and, hence, the electron to proton ratio, depend only weakly on the extent of electron heating at the subshock. The negative feedback also renders the electron spectra insensitive to shock compression ratio and smoothing length scale. The estimated e/p ratio at GeV is between approximately 1%-10%.
Document ID
19950038786
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Levinson, Amir
(California Inst. of Technology, Pasadena, CA United States)
Date Acquired
August 16, 2013
Publication Date
May 1, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 426
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A70385
Funding Number(s)
CONTRACT_GRANT: NAGW-2372
CONTRACT_GRANT: NAGW-2816
Distribution Limits
Public
Copyright
Other

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