Isobe, Hiroaki, Masahito Kubo, Takashi Minoshima, Kiyoshi Ichimoto, Yukio Katsukawa, Theodore D. Tarbell, Saku Tsuneta, Thomas E. Berger, Bruce Lites, Shin'ichi Nagata, Toshifumi Shimizu, Richard A. Shine, Yoshinori Suematsu, and Alan M. Title, Flare Ribbons Observed with G-band and FeI 6302Å, Filters of the Solar Optical Telescope on Board Hinode, Publications of the Astronomical Society of Japan, 59, S807 (2007) (ADS)
(click on the image for a larger version)
Date: 2012 June 04
Update: 2012 November 24
Simple and to the point, this cartoon illustrates the idea that an excitation in the chromosphere would correspond to a diffuse illumination of the photosphere below, implying a different structure for EUV/SXR "backwarming" as a source of white-light flare emission. For a more elaborate cartoon, pointing to a paper with several mechanisms, see Svanda. The S and N here refer to the ribbon layout in the particular flare observed, namely SOL2006-12-13 (X3.4). Backwarming may or may not be an energetically important mechanism, but it must happen at some level.