UNSPECIFIED (2002) The influence of electron temperature and magnetic field strength on cosmic-ray injection in high Mach number shocks. ASTROPHYSICAL JOURNAL, 570 (2 Part 1). pp. 637-646. ISSN 0004-637X

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Abstract

Electron preacceleration from thermal to mildly relativistic energies in high Mach number shocks ( the injection problem) is an outstanding issue in understanding synchrotron radiation from supernova remnants. At high Alfvenic Mach numbers, collisionless perpendicular shocks reflect a fraction of the upstream ions. This gives rise to two-stream instabilities, which in turn can accelerate ions. However, in astrophysical plasmas, the value of the beta-ratio of kinetic pressure to magnetic pressure is not well known. We have used a particle in cell simulation code to investigate the influence of beta on the shock structure and on the electron acceleration (assuming thermodynamic equilibrium in the undisturbed plasma, beta = beta(i) = beta(e)). Previous simulations at low values of beta showed that the phase space distributions of electrons and ions became highly structured: characteristic holes appear in the electron phase space, and the shock dynamics exhibit reformation processes. However, we find that all these features disappear at higher beta due to the high initial thermal velocity of the electrons. It follows that the electron cosmic-ray injection mechanism depends strongly on, that is, on the electron temperature normalized to the magnetic field upstream.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Journal or Publication Title:	ASTROPHYSICAL JOURNAL
Publisher:	UNIV CHICAGO PRESS
ISSN:	0004-637X
Date:	10 May 2002
Volume:	570
Number:	2 Part 1
Number of Pages:	10
Page Range:	pp. 637-646
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/10970

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