Astron. Astrophys. Suppl. Ser. 139, 311-320
S.D. Bao - H.Q. Zhang - G.X. Ai - M. Zhang
Send offprint request: S.D. Bao
Correspondence to: bshd@sun10.bao.ac.cn
Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, China
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
Received February 9; accepted June 9, 1999
We examine the spatial and temporal relationship between
chromospheric H flares and photospheric current
helicities in active regions.
All of the data were obtained by the vector magnetograph
system at Huairou Solar Observing Station of Beijing Astronomical
Observatory. We focus
our analysis on NOAA Active Region 6233, which was observed on 30
August 1990. The result shows that rapid and substantial changes
of distribution of
current helicity in an area or in its vicinity are most likely to
trigger flares, but no compelling correlation between peaks of current
helicity and
flare sites. Furthermore, we study the influence of flares on helicity
for several other active regions. We find that the time variations of current helicity
in the active regions with highly productive flares are more significant
than those of the poorly flare-productive active regions, and that the magnitude of
current helicity does not always decrease after flares. Therefore we
conclude that the rate of variation of current helicity may be considered as an
indicator of flare activity.
In this paper we describe the specification of the instrumentation and
data used, and we describe the methods for computing helicity.
The noises and errors in
our data are estimated to be at the level.
Key words: Sun: activity -- Sun: flares -- Sun: magnetic fields
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