Flare-related magnetic anomaly with a sign reversal

Jiong Qiu, Dale Gary

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


In this paper we report a significant magnetic anomaly, specifically an apparent sign reversal of magnetic polarities in small areas of Michelson Doppler Imager (MDI) magnetograms during the impulsive phase of an X5.6 flare on 2001 April 6. Three flare kernels were observed to emit ≥50 keV hard X-rays, which are located in strong magnetic fields of order ± 1000-1500 G. We find that the apparent sign reversal began and persisted for a few minutes in all three kernels, in precise temporal and spatial correspondence with the hard X-ray sources. We search for a combination of instrumental and flare-induced line profile effects that can account for this behavior. Our studies provide a viable scenario that the observed transient sign reversal is likely to be produced by distorted measurements when the Ni I 6768 Å line comes into emission or strong central reversal as a result of nonthermal beam impact on the atmosphere in regions of strong magnetic fields.

Original languageEnglish (US)
Pages (from-to)615-625
Number of pages11
JournalAstrophysical Journal
Issue number1 I
StatePublished - Dec 10 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Sun: X-rays, gamma rays
  • Sun: activity
  • Sun: flares
  • Sun: magnetic fields


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