Kontar, E.P., Hannah, I.G., and MacKinnon, A.L. (2008) Chromospheric magnetic field and density structure measurements using hard X-rays in a flaring coronal loop. Astronomy and Astrophysics, 489 (3). L57-L60. ISSN 0004-6361 (doi:10.1051/0004-6361:200810719)
Publisher's URL: http://dx.doi.org/10.1051/0004-6361:200810719
Aims: A novel method of using hard X-rays as a diagnostic for chromospheric density and magnetic structures is developed to infer sub-arcsecond vertical variation of magnetic flux tube size and neutral gas density.
Methods: Using Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) X-ray data and the newly developed X-ray visibilities forward fitting technique we find the FWHM and centroid positions of hard X-ray sources with sub-arcsecond resolution (~0.2'') for a solar limb flare. We show that the height variations of the chromospheric density and the magnetic flux densities can be found with an unprecedented vertical resolution of ~150 km by mapping 18-250 keV X-ray emission of energetic electrons propagating in the loop at chromospheric heights of 400-1500 km.
Results: Our observations suggest that the density of the neutral gas is in good agreement with hydrostatic models with a scale height of around 140 30 km. FWHM sizes of the X-ray sources decrease with energy suggesting the expansion (fanning out) of magnetic flux tubes in the chromosphere with height. The magnetic scale height B(z)(dB/dz)-1 is found to be of the order of 300 km and a strong horizontal magnetic field is associated with noticeable flux tube expansion at a height of ~900 km.
|Glasgow Author(s):||MacKinnon, Dr Alexander and Kontar, Dr Eduard and Hannah, Dr Iain|
|Authors:||Kontar, E.P., Hannah, I.G., and MacKinnon, A.L.|
|College/School:||College of Social Sciences > School of Education|
|Journal Name:||Astronomy and Astrophysics|
|Copyright Holders:||Copyright © 2008 EDP Sciences|
|First Published:||First published in Astronomy and Astrophysics 489(3):L57-L60|
|Publisher Policy:||Reproduced in accordance with the copyright policy of the publisher|