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Astron. Astrophys. 319, L17-L20 (1997)


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Letter to the Editor

The effects of high-frequency Alfvén waves on coronal heating and solar wind acceleration

E. Marsch 1 and C.-Y. Tu 1, 2

1 Max-Planck-Institut für Aeronomie, Postfach 20, D-37189 Katlenburg-Lindau, Germany
2 Department of Geophysics, Peking University, Beijing, 100871, PR China

Received 31 October 1996 / Accepted 28 November 1996

Abstract

Wave effects in a two-fluid model for the solar corona and wind are studied. Heating and acceleration are achieved by high-frequency Alfvén waves, which are assumed to be created through small-scale reconnections in the chromospheric network. The wave energy flux [FORMULA] is given in the model as a lower boundary condition. Waves with a power spectrum of the form [FORMULA] in the frequency range from 1 to 800 Hz and with [FORMULA]  nT2 /Hz and [FORMULA]  Hz, corresponding to an integrated amplitude of 35 km/s, can heat the corona to a temperature of [FORMULA]  K at [FORMULA], and [FORMULA] K (the maximum) at [FORMULA], starting from [FORMULA]  K at [FORMULA]. Thermal and wave pressure gradients accelerate the wind to speeds of 100 km/s at [FORMULA], and 212 km/s at [FORMULA], starting from 2 km/s at [FORMULA] in a rapidly diverging stream tube. Asymptotic wind speeds in the observed range of 700 to 800 km/s at 0.3 AU are obtained with wave amplitudes of 30 to 37 km/s in the frequency range from 1 to 30 Hz, corresponding to [FORMULA]  nT2 /Hz.

Key words: Sun: corona, solar wind

Send offprint requests to: E. Marsch

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998

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