Poster abstract details
First-order Fermi acceleration of relativistic particles in nonuniform magnetic fields with nonvanishing
Alfvenic cross helicity turbulence
Abstract
We demonstrate that the combination of adiabatic focusing in a large-scale nonuniform guide magnetic field
and scattering in Alfvenic plasma turbulence with net cross helicity leads to efficient 1st order Fermi
acceleration of energetic charged particles in magnetised cosmic sources. In a diverging guide magnetic
field structure (as upstream of shock waves, or in the halo of galaxies) a majority of backward moving Alfven
waves is required; in a converging guide magnetic field (as in solar and stellar coronal loops) a majority of
forward moving Alfben waves is required. The relevant particle transport equation is solved analytically for
different magnetic guide field variations. It is shown that in the Galaxy cosmic ray hadrons are preferentially
accelerated over a ten orders of magnitude wide momentum range from 0.1 to 10$^9$ GeV/c.
and scattering in Alfvenic plasma turbulence with net cross helicity leads to efficient 1st order Fermi
acceleration of energetic charged particles in magnetised cosmic sources. In a diverging guide magnetic
field structure (as upstream of shock waves, or in the halo of galaxies) a majority of backward moving Alfven
waves is required; in a converging guide magnetic field (as in solar and stellar coronal loops) a majority of
forward moving Alfben waves is required. The relevant particle transport equation is solved analytically for
different magnetic guide field variations. It is shown that in the Galaxy cosmic ray hadrons are preferentially
accelerated over a ten orders of magnitude wide momentum range from 0.1 to 10$^9$ GeV/c.