FLARE ACTIVITY AND MAGNETIC HELICITY INJECTION BY PHOTOSPHERIC HORIZONTAL MOTIONS
Yong-Jae Moon Submitted: 2002-04-04 14:55
We present observational
evidence that the occurrence of homologous flares
in an active region is physically related to
the injection of magnetic helicity by
horizontal photospheric motions. We have analyzed
a set of 1 minute cadence magnetograms of NOAA AR 8100
taken over a period of 6.5 hours by Michelson Doppler Imager (MDI)
on board Solar and Heliospheric Observatory (SOHO).
During this observing time span,
seven homologous flares took place in the active region.
We have computed the magnetic helicity injection rate into
the solar atmosphere by photospheric shearing motions, and
found that a significant amount of magnetic helicity was
injected during the observing period.
In a strong M4.1 flare,
the magnetic helicity injection rate impulsively increased
and peaked at the same time as the X-ray flux did.
The flare X-ray flux integrated over the X-ray emission
time strongly correlates with the magnetic
helicity injected during the flaring interval.
The integrated X-ray flux is found to be a
logarithmically increasing function of
the injected magnetic helicity.
Our results suggest that injection of helicity and
abrupt increase of helicity magnitude play a
significant role in flare triggering.
Authors: Y.-J. MOON, JONGCHUL CHAE, G. S. CHOE, HAIMIN WANG, Y. D. PARK, H. S. YUN, VASYL YURCHYSHYN, PHILIP R. GOODE
Publication Status: ApJ, 574, 1066
Last Modified: 2002-08-15 16:55