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Long period oscillations in sunspots

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Chorley, N., Hnat , B., Nakariakov, Valery M., Inglis, Andrew R. and Bakunina, I. A.. (2010) Long period oscillations in sunspots. Astronomy & Astrophysics, Vol.513 (No.A27). ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361/200913683

Abstract

Long period oscillations of the gyroresonant emission from sunspot atmospheres are studied. Time series data generated from the sequences of images obtained by the Nobeyama Radioheliograph operating at a frequency of 17 GHz for three sunspots have been analysed and are found to contain significant periods in the range of several tens of minutes.Wavelet analysis shows that these periods are persistent throughout the observation periods. The presence of the oscillations is confirmed by several methods (periodogram, wavelets, Fisher randomisation and empirical mode decomposition). Spatial analysis using the techniques of period, power, correlation and time lag mapping reveals regions of enhanced oscillatory power in the umbral regions. Also seen are two regions of coherent oscillation of about 25 pixels in size, that oscillate in anti-phase with each other. Possible interpretation of the observed periodicities is discussed, in terms of the shallow sunspot model and the leakage of the solar g-modes.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Sunspots, Solar oscillations
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	April 2010
Volume:	Vol.513
Number:	No.A27
Identification Number:	10.1051/0004-6361/200913683
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Royal Society (Great Britain), Engineering and Physical Sciences Research Council (EPSRC), Shibasaki, K. (Kiyoto)
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URI:	http://wrap.warwick.ac.uk/id/eprint/3420