The relationship between the sudden change of the Lorentz force and the magnitude of associated flares

Document Type

Article

Publication Date

9-20-2012

Abstract

The rapid and irreversible change of photospheric magnetic fields associated with flares has been confirmed by many recent studies. These studies showed that the photospheric magnetic fields respond to coronal field restructuring and turn to a more horizontal state near the magnetic polarity inversion line (PIL) after eruptions. Recent theoretical work has shown that the change in the Lorentz force associated with a magnetic eruption will lead to such a field configuration at the photosphere. The Helioseismic Magnetic Imager has been providing unprecedented full-disk vector magnetograms covering the rising phase of the solar cycle 24. In this study, we analyze 18 flares in four active regions, with GOES X-ray class ranging from C4.7 to X5.4. We find that there are permanent and rapid changes of magnetic field around the flaring PIL, the most notable of which is the increase of the transverse magnetic field. The changes of fields integrated over the area and the derived change of Lorentz force both show a strong correlation with flare magnitude. It is the first time that such magnetic field changes have been observed even for C-class flares. Furthermore, for seven events with associated coronal mass ejections (CMEs), we use an estimate of the impulse provided by the Lorentz force, plus the observed CME velocity, to estimate the CME mass. We find that if the timescale of the back reaction is short, i.e., in the order of 10s, the derived values of CME mass (∼1015g) generally agree with those reported in literature. © 2012 The American Astronomical Society. All rights reserved.

Identifier

84866092658 (Scopus)

Publication Title

Astrophysical Journal Letters

External Full Text Location

https://doi.org/10.1088/2041-8205/757/1/L5

e-ISSN

20418213

ISSN

20418205

Issue

1

Volume

757

Grant

0745744

Fund Ref

National Science Foundation

This document is currently not available here.

Share

COinS