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Publication

Compensated-current instability of kinetic Alfven waves

Journal Contribution - Journal Article

© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We study a non-resonant instability of kinetic Alfvén waves (KAWs) driven by compensated currents. Such currents set up in response to energetic ion beams occurring in many space and astrophysical plasmas, like foreshock regions in the solar wind and around supernova remnants. Kinetic effects of the background ion gyroradius make the KAW instability stronger than its magnetohydrodynamic (MHD) counterpart and shift its maximum to shorter wavelengths. The KAW growth time can be very short, approaching the proton gyroperiod in the terrestrial foreshock ahead of the quasi-perpendicular bow shock region. The oblique Alfvén instability driven by the cosmic rays in the interstellar and intergalactic plasmas develops mostly in the MHD regime and can extend in the KAW regime only at large fluxes of cosmic rays. Short cross-field wavelengths of growing Alfvén modes facilitate stochastic cross-field acceleration of cosmic rays.
Journal: Monthly Notices of the Royal Astronomical Society
ISSN: 0035-8711
Issue: 4
Volume: 452
Pages: 4236 - 4246
Publication year:2015