Seminars

Lecturer: Dr Mark E Dieckmann (LiU)
Date: 2008-01-24 10:30
Place: Aniara

Relativistically colliding plasma

Relativistically colliding plasma is modelled by PIC simulations in one and two spatial dimensions, taking an ion-to-electron mass ratio of 400 and a temperature of 100 keV. The energy of an initial quasi-parallel magnetic field is one percent of the plasma kinetic energy. Energy dissipation by a growing wave pulse of mixed polarity, probably an oblique whistler wave, and different densities of the colliding plasma slabs result in the forming of an energetic electromagnetic structure during milliseconds. The structure, which develops for an initial collision speed of 0.9 c, accelerates electrons to Lorentz factors of several hundred. A downstream region forms, separating the forward and reverse shocks. In this region, the plasma approaches an energy equi-partition between electrons, ions and the magnetic field. The electron energy spectrum N(E) resembles a power-law at high energies with an exponent close to -2.7 or N(E) $propto E^{-2.7}$. The magnetic field reflects upstream ions, which form a beam and drag the electrons along to preserve the plasma quasi-neutrality. The forward and reverse shocks are asymmetric due to the unequal slab densities. The forward shock may be representative for the internal shocks of gamma ray bursts.

Created 2007-11-21 14:15:03 by Mats Holmström
Last changed 2007-11-21 14:15:03 by Mats Holmström