Multi-wavelength study of a high velocity event near a sunspot

¹ Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland, UK e-mail: jgd@star.arm.ac.uk
² Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India

Received: 27 September 2005
Accepted: 17 November 2005

Abstract

Context.Jets with velocities higher than 200 km s^-1 are often observed in the X-ray spectral range in the solar atmosphere, however, very few such objects are observed in the EUV range.

Aims.We report on an eruptive event observed in the south-west side of a sunspot, within active region, AR0554, in a range of spectral lines formed in the transition region and corona.

Methods.The main data were time-series observations obtained with the Coronal Diagnostic Spectrometer (CDS), in addition to images from the Michelson Doppler Imager (MDI) and Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory. Additional high resolution images from the Transition Region and Coronal Explorer (TRACE) were also used.

Results.The event brightened a loop connecting the sunspot and a bright-point structure, triggering both a high-speed flow in the loop and a transient, low-speed ambient flow into the sunspot. The energy released is quickly conducted to the chromosphere, as deduced from the TRACE 1600 Å images and the light curve of He i 522 Å  as seen by CDS. The results from our multi-wavelength study further indicates that the effect of the eruptive event may have reached temperatures higher than K. Relative Doppler velocities of over 300 km s^-1 were detected in the transition region line, O v 629 Å.

Conclusions.The multi-wavelength analysis indicates that the event is likely due to fast magnetic reconnection in the transition region. The velocities detected are consistent with the results obtained by the evaporation jet model.