EDP Sciences
Free access
Volume 476, Number 2, December III 2007
Page(s) 971 - 977
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20077916

A&A 476, 971-977 (2007)
DOI: 10.1051/0004-6361:20077916

Twisting flux tubes as a cause of micro-flaring activity

D. B. Jess1, 2, R. T. J. McAteer2, M. Mathioudakis1, F. P. Keenan1, A. Andic1, and D. S. Bloomfield3

1  Astrophysics Research Centre, School of Mathematics and Physics, Queen's University, Belfast, BT7 1NN, Northern Ireland, UK
    e-mail: djess01@qub.ac.uk
2  NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771, USA
3  Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany

(Received 21 May 2007 / Accepted 13 September 2007)

High-cadence optical observations of an H-$\alpha$ blue-wing bright point near solar AR NOAA 10794 are presented. The data were obtained with the Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly developed camera system, the RAPID DUAL IMAGER. Wavelet analysis is undertaken to search for intensity-related oscillatory signatures, and periodicities ranging from 15 to 370 s are found with significance levels exceeding 95%. During two separate microflaring events, oscillation sites surrounding the bright point are observed to twist. We relate the twisting of the oscillation sites to the twisting of physical flux tubes, thus giving rise to reconnection phenomena. We derive an average twist velocity of 8.1 km s-1 and detect a peak in the emitted flux between twist angles of $180^{\circ}$ and $230^{\circ}$.

Key words: waves -- Sun: activity -- Sun: evolution -- Sun: flares -- Sun: oscillations -- Sun: photosphere

© ESO 2007