Damping and nonlinear wave-particle interactions of Alfvén-waves in the solar wind |
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| Authors: | Martin A Lee Heinrich J Völk |
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| Institution: | (1) Institut für extraterrestrische Physik, Max-Planck-Institut für Physik und Astrophysik, Garching b. München, Germany |
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| Abstract: | Since most Alfvén-waves in the solar wind are observed to come from the Sun, nonlinear wave-particle interactions can be expected to constitute their dominant dissipation process. The growth or damping of two circularly-polarized Alfvén-waves with wave vectors parallel to the ambient magnetic field is calculated using kinetic theory. If the waves are oppositely polarized they both damp proportional to their frequency. If the waves are of the same polarization, both the lower frequency wave and the plasma particles gain energy at the expense of the higher frequency wave. Thus, with increasing distance from the Sun, a steepening of the power spectrum is expected. For waves propagating in the same direction, the interaction is negligible for small  , while it becomes appreciable for  10–1. For conditions typical of the solar wind near 1 AU an observed half-hour linearly-polarized wave, for example, with  B=0(B
0) has a damping time of about 10 h. |
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