The variation of relative magnetic helicity around major flares

Sung Hong Park, Jeongwoo Lee, G. S. Choe, Jongchul Chae, Hyewon Jeong, Guo Yang, Ju Jing, Haimin Wang

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

We have investigated the variation of magnetic helicity over a span of several days around the times of 11 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) × 1042 Mx2 over a long period (0.5 to a few days). Another finding is that the helicity accumulates at a nearly constant rate, (4.5-48) × 1040 Mx2 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 timeintegrated soft X-ray 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.

Original languageEnglish (US)
Pages (from-to)1397-1403
Number of pages7
JournalAstrophysical Journal
Volume686
Issue number2
DOIs
StatePublished - Oct 20 2008

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Sun: flares
  • Sun: magnetic fields

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