Eclipse observations of high-frequency oscillations in active region coronal loops

¹ Department of Pure and Applied Physics, Queen's University Belfast, Belfast, BT7 1NN, UK
² Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
³ L-3 Communications EER Systems Inc., NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴ School of Computer Science, Queen's University Belfast, Belfast BT7 1NN, UK
⁵ Observatoire Astronomique de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France

Corresponding author: A. C. Katsiyannis, A.Katsiyannis@qub.ac.uk

Received: 20 August 2002
Accepted: 20 March 2003

Abstract

One of the mechanisms proposed for heating the corona above solar active regions is the damping of magnetohydrodynamic (MHD) waves. Continuing on previous work, we provide observational evidence for the existence of high-frequency MHD waves in coronal loops observed during the August 1999 total solar eclipse. A wavelet analysis is used to identify twenty arcsec² areas showing intensity oscillations. All detections lie in the frequency range 0.15–0.25 Hz (7–4 s), last for at least 3 periods at a confidence level of more than 99% and arise just outside known coronal loops. This leads us to suggest that they occur in low emission-measure or different temperature loops associated with the active region.