Theory of quadrupolar sunspots and the active region of August, 1972

Autor: Hou-Mei Chang, Hai-Shou Yang, J. W. Harvey
Rok vydání: 1983
Předmět:
Zdroj: Solar Physics. 84:139-151
ISSN: 1573-093X
0038-0938
DOI: 10.1007/bf00157453
Popis: It is pointed out that energy is stored when the force-free magnetic field in an active region departs from a potential field, the departure manifesting itself as a shear in the field. When the field untwists, energy will immediately be released to produce flares. On the basis of this idea, an analytical solution of the equation of a force-free field is derived under the assumption of a constant force-free factor, and expressions are found for seven important quantities for quadrupole sunspots. These are the magnetic energy of the twisted field, the magnetic energy of the potential field, the extractable free energy (delta M), the magnetic flux, the total current, the force-free factor and the field decay factor. The quantities are expressed in terms of three observables: the field intensity, the twist angle and the distance between two spots of the same polarity. The expression for delta M may have applicability in solar prediction work. For the active region of August 1972, delta M is found to be up to 6 x 10 to the 32nd erg, which is sufficient to supply the energy of the observed flare activity.
Databáze: OpenAIRE
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