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Energy buildup in sheared force-free magnetic fieldsPhotospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.
Document ID
19920055106
Document Type
Reprint (Version printed in journal)
Authors
Wolfson, Richard (Middlebury College VT, United States)
Low, Boon C. (High Altitude Observatory Boulder, CO, United States)
Date Acquired
August 15, 2013
Publication Date
May 20, 1992
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 391
Issue: 1 Ma
ISSN: 0004-637X
Subject Category
SOLAR PHYSICS
Funding Number(s)
CONTRACT_GRANT: NAGW-2141
CONTRACT_GRANT: NSF AST-85-20557
Distribution Limits
Public
Copyright
Other