Studies on a very flare-active δ group: Peculiar δ spot evolution and inferred subsurface magnetic rope structure
- 59 Downloads
The complex subsurface magnetic rope structure of a very flare-active isolated δ group (McMath 13043, July 1974) is studied by means of high-resolution evolutionary data from BBSO magnetic and velocity data. This group showed unusually fast evolution accompanied by a number of intense flares occurring on the neutral line of a δ spot, and provided an excellent opportunity to study the inherent relation of flare occurrence to changes of the magnetic configuration. We first examine the abnormal evolution of this group started by formation of a large, compact, reversed δ spot by squeezing of multipoles. The δ configuration was deformed by penetration into the opposite polarity umbra and its subsequent disappearance, decaying by rapid shear motions. Strong transverse fields over 4000 G were detected in the penumbrae and some umbral components.
Combining these data with the August 1972 region, the evolution of these isolated δ groups is shown to decompose into two flare-associated elementary modes: (A) shearing produced by spot growth and (B) reduction of shear as spots disappear. We propose a model of an emerging twisted magnetic knot to explain the two modes and apply realistically to the present evolution. The inferred magnetic topological structure of this region consists of tightly twisted (sheet-like) knots and a long-winding twisted rope with an internally reversed loop and a hooked bottom struture. Their consecutive emergences are suggested to explain the abnormal evolution of this 5 group. This result indicates that the origin of the concentrated flare activity in these isolated δ groups may be traced to internal magnetic activity responsible for forming anomalous magnetic ropes.
KeywordsFlare Neutral Line Abnormal Evolution Flare Activity Strong Transverse
Unable to display preview. Download preview PDF.
- Bruzek, A.: 1960, Z. Astrophys. 50, 110.Google Scholar
- Bruzek, A.: 1967, Solar Phys. 2, 451.Google Scholar
- Ellison, M. A., McKenna, S. M. P. and Reid, J. H.: 1960, Observatory 80, 149.Google Scholar
- Hagyard, M. J., Smith, J. B., Teuber, D., and West, E. A.: 1984, Solar Phys. 91, 115.Google Scholar
- Kunzel, H.: 1960, Astron. Nachr. 285, 271.Google Scholar
- Livingston, W.: 1974, Proc. Flare-Related Magnetic Field Dynamics, Conference in Boulder, HAO-NCAR, p. 269.Google Scholar
- McIntosh, P.: 1969, World Data Center A, Rep. UAG-5, p. 14.Google Scholar
- McIntosh, P.: 1970, World Data Center A, Rep. UAG-5, p. 22.Google Scholar
- Sakurai, K.: 1972, Solar Phys. 23, 142.Google Scholar
- Sawyer, C. and Smith, S.: 1970, World Data Center A, Rep. UAG-9, p. 9.Google Scholar
- Tanaka, K.: 1980, in R. F. Donnelly (ed.), Solar-Terrestrial Predictions Proceedings, NOAA-ERL, 3, C1.Google Scholar
- Tang, F.: 1983, Solar Phys. 89, 43.Google Scholar
- Warwick, C.: 1966, Astrophys. J. 145, 215.Google Scholar
- Zirin, H.: 1988, Astrophysics of the Sun, Cambridge University Press, Cambridge, p. 321.Google Scholar
- Zirin, H. and Liggett, M. A.: 1987, Solar Phys. 113, 267.Google Scholar
- Zirin, H. and Tanaka, K.: 1973, Solar Phys. 32, 173.Google Scholar