A Revisit of the Masuda Flare

Document Type

Article

Publication Date

3-1-2011

Abstract

We revisit the flare that occurred on 13 January 1992, which is now universally termed the "Masuda flare". The new analysis is motivated not just by its uniqueness despite the increasing number of coronal observations in hard X-rays, but also by the improvement of Yohkoh hard X-ray image processing, which was achieved after the intensive investigations on this celebrated event. Using an uncertainty analysis, we show that the hard X-ray coronal source is located closer to the soft X-ray loop by about 5000 km (or 7 arcsec) in the re-calibrated Hard X-ray Telescope (HXT) images than in the original ones. Specifically, the centroid of the M1-band (23 - 33 keV) coronal source is above the maximum brightness of the Soft X-ray Telescope (SXT) loop by 5000±1000 km (9600 km in the original data) and above the apex of the SXT loop represented by the 30% brightness contour by 2000±1000 km (~ 7000 km in the original data). The change is obviously significant, because most coronal sources are above the thermal loop by less than 6 arcsec. We suggest that this change may account for the discrepancy in the literature, i. e., the spectrum of the coronal emission was reported to be extremely hard below ~ 20 keV in the pre-calibration investigations, whereas it was reported to be considerably softer in the literature after the re-calibration done by Sato, Kosugi, and Makishima (Pub. Astron. Soc. Japan51, 127, 1999). Still, the coronal spectrum is flatter at lower energies than at higher energies, due to the lack of a similar, co-spatial source in the L-band (14 - 23 keV), for which a convincing explanation is absent. © 2010 Springer Science+Business Media B.V.

Identifier

79951770124 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1007/s11207-010-9688-z

e-ISSN

1573093X

ISSN

00380938

First Page

67

Last Page

82

Issue

1

Volume

269

Grant

ATM-0849453

Fund Ref

National Science Foundation

This document is currently not available here.

Share

COinS