Velocity-space diffusion of solar wind protons in oblique waves and weak turbulence
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 the quasi-linear theory be described as a diffusion process. The impact this diffusio...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2011-11-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/29/2089/2011/angeo-29-2089-2011.pdf |
| Summary: | 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 the quasi-linear
theory be described as a diffusion process. The impact this diffusion 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 on 14
April 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 be well explained by cyclotron-resonant diffusion of the protons in
oblique fast magnetoacoustic and Alfvén waves propagating away from the
Sun. |
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| ISSN: | 0992-7689 1432-0576 |