Sunspots and the Physics of Magnetic Flux Tubes. VII. Heat Flow in a Convective Downdraft
Abstract
The heat flux in the familiar Boussinesq convective cell with free upper and lower boundaries is plotted to show the suppression of the upward heat flow by a downdraft. Application to the solar convective zone shows that downdrafts of 1-2 km 1 at depths of 1 x 1O km beneath the visible surface of the Sun are sufficient to reduce the upward heat flux to a small fraction of the ambient value. Hence the downdraft that is postulated to operate beneath the sunspot, to account for the gathering of flux tubes to form the spot, would be sufficient to reduce the heat flux to values comparable to those observed in sunspot umbrae. This greatly relieves the demands on cooling by the convective generation of Alfve'n waves in order to form the observed intense fields of 3000 gauss or more. Subject headings: convection - hydromagnetics - Sun: sunspots
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1979
- DOI:
- 10.1086/157288
- Bibcode:
- 1979ApJ...232..291P