Evolutionary Characteristics of Magnetic Helicity Injection in Active
Regions
Hyewon Jeong and Jongchul Chae
Magnetic helicity is now regarded as an important physical
quantity in understanding the magnetic activities of solar
active regions such as flares and coronal mass ejections.
A common wisdom is that magnetic helicity is transported
from the interior to the corona, and then to the interplanetary
space. In the present study, we are interested in examining
tempposter behavior of helicity injection through the photospheric
boundary that divides the interior and the corona. Specifically
we aim to see whether magnetic helicity is supplied to the
corona in a more or less steady way or not. We determined
the rate of helicity injection in each active region applying
Chae's method to the full-disk, 96 minute-cadence magnetograms
taken by SOHO/MDI. Using these data, each active region could
be followed without interruption for about 5 days while they
were away from the limb. Some active regions were followed at
next rotations, too. We found that magnetic helicity was
supplied intensively during the period of flux emergence,
especially during the growth of active regions. The amount
of helicity injected during the growth period ranged from
2 x 10^42 Mx^2 to 40 x 10^42 Mx^2, depending on the active
region flux. These values are much larger than the estimated
contributions of differential rotation at the photospheric
level. Our result suggests that most of the magnetic helicity
in active regions may be supplied for several days during the
early phase of the active regions.
Correspondence
Hyewon Jeong (hwjung@astro.snu.ac.kr), Seoul National University
presentation
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