Particle acceleration at oblique shocks and discontinuities of the density profile
U.D.J. Gieseler 1,
J.G. Kirk 1,
Y.A. Gallant 2 and
A. Achterberg 2
Received 28 October 1998 / Accepted 8 February 1999
In the theory of diffusive acceleration at oblique shock fronts the question of the existence of a discontinuity of energetic particle density is contentious. The resolution of this problem is interesting from a theoretical point of view, and potentially for the interpretation of observations of particle densities at heliospheric shocks and of high-resolution radio observations of the rims of supernova remnants. It can be shown analytically that an isotropic particle distribution at a shock front implies continuity of the particle density - whether or not the shock is oblique. However, if the obliquity of the shock induces an anisotropy, a jump is permitted. Both semi-analytic computations and Monte-Carlo simulations are used to show that, for interesting parameter ranges, a jump is indeed produced, with accelerated particles concentrated in a precursor ahead of the shock front.
Key words: acceleration of particles shock waves methods: numerical ISM: cosmic rays ISM: supernova remnants
Present address: University of Minnesota, Department of Astronomy, 116 Church St. S.E., Minneapolis, MN 55455, USA
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© European Southern Observatory (ESO) 1999
Online publication: April 12, 1999