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The periodic variations of a white-light flare observed with ULTRACAM

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Mathioudakis, M., Bloomfield, D. S., Jess, D. B., Dhillon, V. S. and Marsh, T. R.. (2006) The periodic variations of a white-light flare observed with ULTRACAM. Astronomy & Astrophysics, Vol.456 (No.1). pp. 323-327. ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361:20054752

Abstract

High time resolution observations of a white-light flare on the active star EQ PegB show evidence of intensity variations with a period of ≈10 s. The period drifts to longer values during the decay phase of the flare. If the oscillation is interpreted as an impulsively-excited, standing-acoustic wave in a flare loop, the period implies a loop length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode and the second harmonic, respectively. However, the small loop lengths imply a very high modulation depth making the acoustic interpretation unlikely. A more realistic interpretation may be that of a fast-MHD wave, with the modulation of the emission being due to the magnetic field. Alternatively, the variations could be due to a series of reconnection events. The periodic signature may then arise as a result of the lateral separation of individual flare loops or current sheets with oscillatory dynamics (i.e., periodic reconnection).

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Flare stars, Stars -- Corona -- Magnetic fields, Stellar oscillations
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	September 2006
Volume:	Vol.456
Number:	No.1
Page Range:	pp. 323-327
Identification Number:	10.1051/0004-6361:20054752
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Particle Physics and Astronomy Research Council (Great Britain) (PPARC)
Grant number:	PPA/G/S/2002/00092 (PPARC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/3506