New cosmic ray transport effects from the mirror force in inhomogeneous magnetic fields

• Applicant: Professor Dr. Reinhard Schlickeiser
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 248902482

The parallel component of the mirror force in non-uniform large-scale guide magnetic fields gives rise to coherent convection of cosmic ray particles in particle position and momentum, referred to as adiabatic focusing and focused acceleration. Adiabatic focusing causes spatial particle streaming with a speed $\kapp /L$, given by the ratio of the parallel spatial diffusion coefficient and the focusing length $L$, along the guide field even in a medium at rest. Focused acceleration causes particle convection in momentum space, representing a 1st order Fermi particle acceleration mechanism for negative values of the product $H_cL<0$, where the cross helicity $H_c$ characterizes the excess of forward over backward moving plasma waves in the medium. Positive values of the cross helicity occur particularly in the upstream region of cosmic shock waves, because the upstream precursor distribution function of accelerated cosmic ray particles amplifies (damps) the forward- (backward-) propagating plasma waves. In a converging ($L<0$) guide magnetic field, as expected for the more than 70 galactic supernova remnants in close physical contact with massive molecular clouds, the efficient upstream focused acceleration can explain why they are efficient particle accelerators and strong emitters of high-energy GeV and TeV photons. It is proposed to improve the cosmic ray transport theory in the presence of focused transport and acceleration, provide new analytical solutions for the resulting time-dependent and stationary telegraph transport equation for realistic finite scattering regions, and to explore the favorable conditions for efficient particle acceleration in cosmic shock waves near massive molecular clouds. A further application is concerned with the explanation of the rising positron fraction in galactic cosmic rays.

• DFG Programme: Research Grants