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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 2
Nonlin. Processes Geophys., 15, 295–304, 2008
https://doi.org/10.5194/npg-15-295-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Nonlinear waves and turbulence in space

Nonlin. Processes Geophys., 15, 295–304, 2008
https://doi.org/10.5194/npg-15-295-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  26 Mar 2008

26 Mar 2008

Coronal heating and wind acceleration by nonlinear Alfvén waves – global simulations with gravity, radiation, and conduction

T. K. Suzuki T. K. Suzuki
  • School of Arts and Sciences, University of Tokyo, Komaba, Meguro, 153-8902 Tokyo, Japan

Abstract. We review our recent results of global one-dimensional (1-D) MHD simulations for the acceleration of solar and stellar winds. We impose transverse photospheric motions corresponding to the granulations, which generate outgoing Alfvén waves. We treat the propagation and dissipation of the Alfvén waves and consequent heating from the photosphere by dynamical simulations in a self-consistent manner. Nonlinear dissipation of Alfven waves becomes quite effective owing to the stratification of the atmosphere (the outward decrease of the density). We show that the coronal heating and the solar wind acceleration in the open magnetic field regions are natural consequence of the footpoint fluctuations of the magnetic fields at the surface (photosphere). We find that the properties of the solar wind sensitively depend on the fluctuation amplitudes at the solar surface because of the nonlinearity of the Alfvén waves, and that the wind speed at 1 AU is mainly controlled by the field strength and geometry of flux tubes. Based on these results, we point out that both fast and slow solar winds can be explained by the dissipation of nonlinear Alfvén waves in a unified manner. We also discuss winds from red giant stars driven by Alfvén waves, focusing on different aspects from the solar wind.

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