Force-free Magnetic Field Extrapolation for the Complex Sunspot Group of August 1972
Abstract
A method for theoretical extrapolation of photospheric longitudinal magnetograms to higher levels for force-free magnetic fields is presented. The method has been used to calculate the magnetic field vector and lines of force in the flare active region of August 1972. Calculated fields are compared with other observations such as structures in H-alpha. Results of August 3 show that the loop prominence systems observed during the flares of August 2 and 4 are represented by a force field with a positive value of alpha, rather than a current-free field. The extractable energy supply of this force-free field is of the order of maximum flare demand (10 to the 32nd erg); the height dependence of the magnetic field strengths agrees with that from radio and X-ray estimates. Similar results are obtained for the August 7 magnetic field structure. It is suggested that the mean magnetic field structure of the active region may be represented by a force-free field much better than by a potential field.
- Publication:
-
Astronomische Nachrichten
- Pub Date:
- 1979
- DOI:
- 10.1002/asna.19793000307
- Bibcode:
- 1979AN....300..151S
- Keywords:
-
- Force-Free Magnetic Fields;
- Magnetic Signatures;
- Photosphere;
- Sunspots;
- Boundary Value Problems;
- Field Strength;
- Field Theory (Physics);
- Magnetic Field Configurations;
- Potential Fields;
- Solar Flares;
- Solar Physics