Evaluating mean magnetic field in flare loops

Document Type

Article

Publication Date

3-1-2009

Abstract

We analyze multiple-wavelength observations of a two-ribbon flare exhibiting apparent expansion motion of the flare ribbons in the lower atmosphere and rising motion of X-ray emission at the top of newly-formed flare loops. We evaluate magnetic reconnection rate in terms of V r B r by measuring the ribbon-expansion velocity (V r) and the chromospheric magnetic field (B r) swept by the ribbons. We also measure the velocity (V t) of the apparent rising motion of the loop-top X-ray source, and estimate the mean magnetic field (B t) at the top of newly-formed flare loops using the relation 〈V t B t〉≈ 〈V r B r〉, namely, conservation of reconnection flux along flare loops. For this flare, B t is found to be 120 and 60 G, respectively, during two emission peaks five minutes apart in the impulsive phase. An estimate of the magnetic field in flare loops is also achieved by analyzing the microwave and hard X-ray spectral observations, yielding B=250 and 120 G at the two emission peaks, respectively. The measured B from the microwave spectrum is an appropriately-weighted value of magnetic field from the loop top to the loop leg. Therefore, the two methods to evaluate coronal magnetic field in flaring loops produce fully-consistent results in this event. © 2009 Springer Science+Business Media B.V.

Identifier

60849089889 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1007/s11207-009-9316-y

e-ISSN

1573093X

ISSN

00380938

First Page

107

Last Page

118

Issue

1

Volume

255

Grant

NNX08AE44G

Fund Ref

National Aeronautics and Space Administration

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