Cross-field current closure below the solar photosphere
Abstract
A simple model is developed to describe how an externally imposed current closes as a function of time below the photosphere. A vertical current density is assumed to turn on at the photospheric boundary. The model implies that the subsequent closure of the current in the sub-photosphere depends only on the ratio RA/R, where RA = muoVA is the Alfvenic impedance of the photosphere and R = 1/sigmaP is the resistance corresponding to the conductivity sigmaP and a characteristic length l. For RA/R much greater than 1, current closure occurs at a front, propagating with the Alfven speed. For RA/R much less than 1, current closure is a diffusive process ahead and behind a slowly propagating Alfvenic front. The first case is the relevant one for the Sun, where RA/R as approximately 108/VA, for VA in kilometers per second.
- Publication:
-
Australian Journal of Physics
- Pub Date:
- 1994
- DOI:
- 10.1071/PH940361
- Bibcode:
- 1994AuJPh..47..361W
- Keywords:
-
- Closures;
- Cross Flow;
- Current Distribution;
- Mathematical Models;
- Photosphere;
- Solar Physics;
- Sun;
- Current Density;
- Electrical Properties;
- Impedance;
- Magnetohydrodynamic Waves;
- Magnetohydrodynamics;
- Solar Physics