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Jeongwoo Lee   Submitted: 2008-08-21 13:48

We have investigated the variation of magnetic helicity over a span of several days around the times of eleven X-class flares which occurred in seven active regions (NOAA 9672, 10030, 10314, 10486, 10564, 10696, and 10720) using the magnetograms taken by the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO). As a major result we found that each of these major flares was preceded by a significant helicity accumulation, (1.8?16)x1042 Mx^2 over a long period (0.5?a few days). Another finding is that the helicity accumulates at a nearly constant rate, (4.5?48)x1040 Mx^2 hr-1, and then becomes nearly constant before the flares. This led us to distinguish the helicity variation into two phases: a phase of monotonically increasing helicity and the following phase of relatively constant helicity. As expected, the amount of helicity accumulated shows a modest correlation with time-integrated soft Xray flux during flares. However, the average helicity change rate in the first phase shows even stronger correlation with the time-integrated soft X-ray flux. We discuss the physical implications of this result and the possibility that this characteristic helicity variation pattern can be used as an early warning sign for solar eruptions.

Authors: Sung-Hong Park, Jeongwoo Lee, G.S. Choe, Jongchul Chae, Hyewon Jeong, Guo Yang, Ju Jing, Haimin Wang
Projects: None

Publication Status: To appear in ApJ, 2008 October 1 issue
Last Modified: 2008-08-21 13:48
Go to main E-Print page  Nonlinear theory of resonant slow waves in anisotropic and dispersive plasmas  THE VARIATION OF RELATIVE MAGNETIC HELICITY
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