Non-linear spherical Alfvén waves |
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Authors: | UlfTorkelsson G. ChristopherBoynton |
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Affiliation: | Institute of Astronomy, Madingley Road, Cambridge CB3 0HA; Physics Department, University of Miami, PO Box 248046, Coral Gables, FL 33124, USA |
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Abstract: | We present a one-dimensional numerical study of Alfvén waves propagating along a radial magnetic field. Neglecting losses, any spherical Alfvén wave, no matter how small its initial amplitude is, becomes non-linear at sufficiently large radii. From previous simulations of Alfvén waves in plane-parallel atmospheres we expected the waves to steepen and produce current sheets in the non-linear regime, which was confirmed by our new calculations. On the other hand we found that even the least non-linear waves were damped out almost completely before 10 R⊙. A damping of that kind is required by models of Alfvén wave driven winds from old low-mass stars as these winds are mainly accelerated within a few stellar radii. |
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Keywords: | MHD waves solar wind stars: mass-loss |
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