Summary: Astronomy & Astrophysics manuscript no. 3826 September 27, 2005
(DOI: will be inserted by hand later)
Repetitive occurrence of explosive events at a coronal hole
J. G. Doyle 1 , M. D. Popescu 1,2 and Y. Taroyan 1
1 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
2 Astronomical Institute of the Romanian Academy, RO040557 Bucharest 28, Romania
Received / accepted
Abstract. SUMER/SoHO data taken at a coronal hole boundary show a repetitive explosive event occurrence rate of around
3 min increasing to over 5 min towards the end of the activity. We suggest that the neighbouring oppositely directed closed
and open field lines at the coronal hole boundary undergo repetitive reconnection seen as a sequence of explosive events.
The repetitive reconnection may be triggered by transverse oscillations of the flux tubes in the closed field line region. These
oscillations periodically separate and bring together the closed and open field lines on the two sides of the coronal hole boundary.
An important indicator favouring the interpretation in terms of a kink mode is the observed increase in the oscillation period.
Key words. Sun: activity: -- Sun: oscillations -- Sun: transition region -- Sun: UV radiation -- Line: profiles
Explosive events (also called bidirectional jets) are small re
gions of a few arcseconds size with strong blue and redshifted
emission reaching Doppler shifts of up to 150 km s -1 . Over the
past decade, there have been many studies of explosive event