The Effects on Mass Flows on the Dissipation of Alfven Waves in the Upper Layers of the Solar Atmosphere
Abstract
The influence of parallel plasma flows on the propagation of shear Alfvén waves along magnetic structures is considered. It is shown that even in a simple case of regular mass flows directed along the magnetic field, their presence considerably modifies the dissipation of shear Alfvén waves, affecting both the magnitude and the height of maximum dissipation. The strongest effect occurs in the case of downflows when the flow velocity at a certain height becomes equal to the Alfvén velocity. Near that point, the wave comes to extinction and gives off its energy completely. The axial extent of the absorption region is evaluated. This effect can be directly associated with observed high-velocity downflows in the transition region, and, in particular, can serve as a qualitative explanation for the high variability of the emission observed near 105 K. In the presence of upward mass flows and moderate downflows, the dissipation of phase-mixed Alfvén waves is accompanied by the radial redistribution of the energy input across the magnetic structure, thus creating a mosaic pattern in the emitting regions. The flow velocities are assumed to be below the thresholds which correspond to the onset of hydrodynamic and dissipative instabilities.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1995
- DOI:
- 10.1086/176227
- Bibcode:
- 1995ApJ...451..381R
- Keywords:
-
- MAGNETOHYDRODYNAMICS: MHD;
- PLASMAS;
- SUN: ATMOSPHERE;
- WAVES