Generation of solar Hα impact polarization by fragmented evaporative upflows

Fletcher, L. and Brown, J. (1998) Generation of solar Hα impact polarization by fragmented evaporative upflows. Astronomy and Astrophysics, 338, pp. 737-746.

91466.pdf - Published Version


Publisher's URL:


In this paper a novel mechanism is proposed for the generation of Hα impact polarization observed during some solar flares. Rather than being generated by the primary particle beams transporting energy from the chromosphere to the corona, we suggest that following heating, the solar chromosphere evaporates in a fragmented manner, and that impact excitations in the regions of interaction of hot evaporating and cool non-evaporating material locally generates impact-polarized Hα emission. This thermal upflow model is more consistent with the large areas and times over which polarization is observed than are beam models. A simple model for the process is given, and the resulting polarization is calculated and compared with observations, under two assumptions about the number density of neutral particles in the interaction regions.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Fletcher, Professor Lyndsay and Brown, Professor John
Authors: Fletcher, L., and Brown, J.
Subjects:Q Science > QB Astronomy
Q Science > QC Physics
College/School:College of Science and Engineering > School of Physics and Astronomy
Research Group:Astronomy and Astrophysics
Journal Name:Astronomy and Astrophysics
Journal Abbr.:Astron. Astrophys.
Publisher:EDP Sciences
ISSN (Online):1432-0746
Copyright Holders:Copyright © 1998 EDP Sciences
First Published:First published in Astronomy and Astrophysics 338:737-746
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

University Staff: Request a correction | Enlighten Editors: Update this record