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SYGP: Symposium Gemeinsame Probleme in Fusions- und astrophysikalischen Plasmen

SYGP 3: Contributed Talks

SYGP 3.2: Vortrag

Montag, 12. März 2012, 16:45–17:00, V55.22

Velocity-space diffusion of solar wind protons in oblique waves and weak turbulence — •Eckart Marsch and Sofiane Bourouaine — Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau

The fast solar wind is permeated by all kinds of plasma waves which have a broad range of wavelengths and occur on many different scales. Kinetically, a plasma wave induces ion-wave interactions which can within quasilinear theory be described as a diffusion process. The impact this may have on the shape of the proton velocity distribution function (VDF) is studied. We first analyse theoretically some of the possible kinetic effects of the waves on the ions. Then the model predictions are compared with the detailed in-situ plasma measurements made by the Helios spacecraft in 1976 at 0.3 AU and found to comply favourably with resonant diffusion of protons in obliquely propagating magnetohydrodynamic waves. In particular, the shape at the edges of the VDFs at positive proton velocities in the wind frame can well be explained by cyclotron-resonant diffusion of the protons in oblique fast magnetoacoustic and Alfven waves propagating away from the Sun.