Filament Eruptions During the Period of Sept. 1991 through Sept. 1994

A.E. Komenda (NJIT), H. Wang (NJIT), F. Tang (BBSO, Caltech), and H. Zirin (BBSO, Caltech)

Continuous full disk H-alpha images recorded by Big Bear Solar Observatory (BBSO) from September 1, 1991 to September 12, 1994 (the first three years of Yohkoh mission) were digitized and analyzed. The data set consists of nearly 10,000 H{alpha} images, one every half hour for the period when the BBSO was observing. Three statistical studies of the solar filaments based on this set of data are made: (1) The disk distribution of all larger filaments with a minimum length of 70 arcsec, and the time of their disappearance. Of the 1095 such filaments, 439 disappeared during our continuous observations, 314 disappeared during the BBSO night gap, 162 disappeared during data gap (more than 24 hours) and 180 rotated beyond the West limb. If we plot latitudes as a function of time for all these filaments, it showed a uniform distribution in latitude. However, if we plot the distribution of larger filaments (200 arcsec or above), then the butterfly pattern appears - position of filaments tends to drift to lower latitude as solar activity decreases. (2) The disk distribution of all detectable filaments, large and small, for the 9-months period, January 1994 to September 1994. We find the size distribution of the 351 filaments collected follows a power law with a power index of -1.40. (3) The direct correlation analysis between the filament disappearances and fluctuations in the geomagnetic field.


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