Asymmetric Distribution of Solar X-ray Flares
Hari Om Vats [vats@prl.res.in], Astronomy Astrophysics Division, Physical Research
Laboratory Ahmedabad, India; and Niraj Pandya, Tolani College of Arts and Science,
Adipur, Gujarat, India
Solar flares are generally examined as individual events in great detail. The advent of
spacecraft observations of flares in hard and soft X-rays has provided data sets that are
naturally suited to statistical examination. Statistical studies have brought a new perspective
to flare physics, providing theorists with ideas for the physical mechanism underlying flares.
In particular, the recognition that the frequency distribution of the size of solar flares is a
power law a property flares share with diverse physical phenomena. We pursued a statistical
study of the X-ray flares using X-ray observation of GOES satellites for more than a solar
cycle. The investigations reveal that x-ray flares have preferential location on the solar
surface. Two examples are (1) out of 1077 total number X-ray flares in 1993; 55% occurred
in northern hemisphere. The flare occurrence peaks at ~ 12.5 degree both in north and south.
The peak in the northern hemisphere is considerably higher than that in south. (2) Out of
1962 total number of X-ray flares in 2004; 58% are in the southern hemisphere. Here too
peak occurrence is ~12.5 degree both in north and south, however, southern peak is higher
than that in north. The distribution of peak and average flux during the flares in these years
also have asymmetry, but of opposite sign. The analysis of other years is going on and in this
article we will present these results and discuss their implications.