2005/12/20 by Q. R. Chen, M. D. Ding · 3 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.1086/500635
published as Astrophys.J.641:1217-1221,2006 · 16 pages, 5 figures, accepted for publication in ApJ
arxiv created 2005/12/20 · openalex publication_date 2006/04/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We present observations of the 2002 September 30 white-light flare, in which the optical continuum emission near the Hα line is enhanced by ~10%. The continuum emission exhibits a close temporal and spatial coincidence with the hard X-ray (HXR) footpoint observed by RHESSI . We find a systematic motion of the flare footpoint seen in the continuum emission; the motion history follows roughly that of the HXR source. This gives strong evidence that this white-light flare is powered by heating of nonthermal electrons. We note that the HXR spectrum in 10-50 keV is quite soft with γ ≈ 7 and there is no HXR emission above 50 keV. The magnetic configuration of the flaring region implies magnetic reconnection taking place at a relatively low altitude during the flare. Despite a very soft spectrum of the electron beam, its energy content is still sufficient to produce the heating in the lower atmosphere, where the continuum emission originates. This white-light flare highlights the importance of radiative back-warming to transport the energy below when direct heating by beam electrons is obviously impossible.