Warm thick target solar gamma-ray source revisited

MacKinnon, A.L. and Toner, M. (2003) Warm thick target solar gamma-ray source revisited. Astronomy and Astrophysics, 409(2), 745 -753. (doi: 10.1051/0004-6361:20030943)



Publisher's URL: http://dx.doi.org/10.1051/0004-6361:20030943


The 1.63 MeV gamma-ray line of Ne-20 is sensitive to protons of lower energies than most other nuclear de-excitation lines. Its unexpected strength has been taken as evidence for a solar flare fast ion distribution that remains steep at low energies, and thus has a large total energy content. It has also been suggested that its strength might instead reflect the enhancement of ion lifetimes that occurs when ambient temperatures exceed 10(7) K. Here we revisit this idea ( a) recognising that ions may be effectively trapped in high temperature regions and (b) taking account of the contribution to the line of all ions above threshold. The strength of the 1.63 MeV line relative to other de-excitation lines has been used to estimate the steepness (e.g. energy power-law index) of the ion distribution. We show that these estimates must be significantly revised if primary ions are contained in a region with temperature in the few 10(7) K range, lower than found elsewhere. Such a region would almost certainly be coronal, so we also briefly review other arguments for and against coronal gamma-ray sources.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Toner, Mr Mark and MacKinnon, Dr Alexander
Authors: MacKinnon, A.L., and Toner, M.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN (Online):1432-0746
Copyright Holders:Copyright © 2003 EDP Sciences
First Published:First published in Astronomy and Astrophysics 409(2):745-753
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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