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The effect of ballooning modes on thermal transport and magnetic field diffusion in the solar corona
Author(s) -
Strauss H. R.
Publication year - 1989
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl016i003p00219
Subject(s) - thermal conduction , mechanics , magnetic field , turbulence , physics , pressure gradient , corona (planetary geology) , temperature gradient , joule heating , materials science , thermodynamics , meteorology , quantum mechanics , astrobiology , venus
Presently favored mechanisms of coronal heating ‐ current sheet dissipation and Alfvén wave resonant heating ‐ deposit heat in thin layers. Classical thermal conduction cannot explain how heat is transported across the magnetic field. If heating occurs in thin layers, large pressure gradients can be created, which can give rise to ballooning modes. These instabilities are caused by the pressure gradient and the curvature of the magnetic field, and are stabilized by magnetic tension. The modes are broad band in wavelength and should produce turbulence. A mixing length expression for the turbulent heat transport shows that it is more than adequate to rapidly convect heat into much broader layers. Furthermore, the turbulent resistivity implies that heating occurs over most of the width of these broadened layers. The broadening also implies that much shorter time scales are required for heating. The β values in the corona suggest that 1 ‐ 10 turbulent layers are formed in typical loop or arch structures.