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Paper: Evolutionary Characteristics of Magnetic Helicity Injection in Active Regions
Volume: 369, New Solar Physics with Solar-B Mission
Page: 167
Authors: Jeong, H.; Chae, J.
Abstract: 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 the temporal 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 Chaeís 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 it was 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 1.7 ◊ 1042Mx2 to 43 ◊ 1042Mx2, 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 active region evolution.
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