The automatic predictability of super geomagnetic storms from halo CMEs associated with large solar flares

Document Type

Article

Publication Date

10-1-2006

Abstract

We investigate the relationship between magnetic structures of coronal mass ejection (CME) source regions and geomagnetic storms, in particular, the super storms when the D st index decreases below -200 nT. By examining all full halo CMEs that erupted between 1996 and 2004, we selected 73 events associated with M-class and X-class solar flares, which have a clearly identifiable source region. By analyzing daily full-disk MDI magnetograms, we found that the horizontal gradient of the line-of-sight magnetic field is a viable parameter to identify a flaring magnetic neutral line and thus can be used to predict the possible source region of CMEs. The accuracy of this prediction is about 75%, especially for those associated with X-class flares (up to 89%). The mean orientation of the magnetic structures of source regions was derived and characterized by the orientation angle θ, which is defined to be ≤ 90° in the case of the southward orientation and ≥ 90°, when the magnetic structure is northwardly oriented. The orientation angle was calculated as the median orientation angle of extrapolated field lines relative to the flaring neutral line. We report that for about 92% of super storms (12 out of 13 events) the orientation angle was found to be southward. In the case of intense and moderate storms (D st ≥ -200 nT), the relationship is less pronounced (70%, 21 out of 30 events). Our findings demonstrate that the approach presented in this paper can be used to perform an automatic prediction of the occurrence of large X-class flares and super geomagnetic storms. © Springer Science + Business Media, Inc. 2006.

Identifier

33751034088 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1007/s11207-006-0164-8

e-ISSN

1573093X

ISSN

00380938

First Page

141

Last Page

165

Issue

1

Volume

238

Grant

NAG5-13661

Fund Ref

National Aeronautics and Space Administration

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