Transport and acceleration of particles in astrophysical plasmas
The acceleration of high energy non-thermal cosmic rays depends crucially
on their transport in configuration and momentum space. This transport
results for photons in a Boltzmann equation. The problem of production
of high energy photons in a hot plasma disk is formulated and the corresponding
integro-differential equation is solved. This is done by reduction to an
algebraic eigenvalue problem. Solutions are obtained allowing for an arbitrary
anisotropy of the source function, with no restriction on the optical depth
of the disk. In addition to the spectral index, the method of solution
allows one to determine the spatial and angular dependence of the emergent
radiation. In the case of an optically thin disk, this radiation is strongly
collimated along the disk surface.
The acceleration of charged particles is determined by the external
electromagnetic fields. Supernova remnants are expected to contain stochastic
magnetic fields, which are in some regions directed perpendicular to the
shock normal. Recent analytical results show that the resulting anomalous
transport leads to a steeper spectrum of cosmic rays, than pure diffusive
transport. A Monte-Carlo method is used to examine the transport and the
acceleration. The results are discussed and compared with analytical treatments,
the region of validity, of which is determined.
Udo Gieseler
24. March 1998