Chromospheric magnetic field and density structure measurements using hard X-rays in a flaring coronal loop

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. (doi: 10.1051/0004-6361:200810719)

Abstract

<p><b>Aims:</b> 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.</p> <p><b>Methods:</b> 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.</p> <p><b>Results:</b> 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.</p>

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kontar, Professor Eduard and MacKinnon, Dr Alexander 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
• Publisher: EDP Sciences
• ISSN: 0004-6361
• ISSN (Online): 1432-0746
• 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

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Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
39846	1	Acceleration, propagation and emission of energetic particles from the sun to the earth	Eduard Kontar	Particle Physics & Astronomy Research Council (PPARC)	PP/C001656/1	Physics and Astronomy
46593	1	Solar, stellar and cosmological plasmas: a synthesis of data, modelling and theory.	Declan Diver	Science & Technologies Facilities Council (STFC)	ST/F002149/1	Physics and Astronomy