Robbrecht, E. (Eva), Verwichte, E. (Erwin), Berghmans, D., Hochedez, J. F., Poedts, Stefaan, 1962- and Nakariakov, Valery M.. (2001) Slow magnetoacoustic waves in coronal loops : EIT and TRACE. Astronomy & Astrophysics, Vol.370 (No.2). pp. 591-601. ISSN 0004-6361

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Abstract

On May 13, 1998 the EIT (Extreme ultraviolet Imaging Telescope) on board of SoHO (Solar and Heliospheric Observatory) and TRACE (Transition Region And Coronal Explorer) instruments produced simultaneous high cadence image sequences of the same active region (AR 8218). TRACE achieved a 25 s cadence in the FeIX (171 Å) bandpass while EIT achieved a 15 s cadence (operating in "shutterless mode", SoHO JOP 80) in the FeXII (195 Å) bandpass. These high cadence observations in two complementary wavelengths have revealed the existence of weak transient disturbances in an extended coronal loop system. These propagating disturbances (PDs) seem to be a common phenomenon in this part of the active region. The disturbances originate from small scale brightenings at the footpoints of the loops and propagate along the loops. The projected propagation speeds roughly vary between 65 and 150 km s-1 for both instruments which is close to and below the expected sound speed in the coronal loops. The measured slow magnetoacoustic propagation speeds seem to suggest that the transients are sound (or slow) wave disturbances. This work differs from previous studies in the sense that it is based on a multi-wavelength observation of an entire loop bundle at high cadence by two EUV imagers. The observation of sound waves along the same path shows that they propagate along the same loop, suggesting that loops contain sharp temperature gradients and consist of either concentric shells or thin loop threads, at different temperatures.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Sun -- Corona, Sun -- Loop prominences, Solar oscillations, Magnetohydrodynamic waves
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	May 2001
Volume:	Vol.370
Number:	No.2
Page Range:	pp. 591-601
Identification Number:	10.1051/0004-6361:20010226
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Belgium. Services fédéraux des affaires scientifiques, techniques et culturelles (OSTC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/3822

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