Chromospheric evaporation in sympathetic coronal bright points

¹ Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, CAS, 210008 Nanjing, PR China
e-mail: zhangqm@pmo.ac.cn
² Key Lab of Modern Astronomy and Astrophysics, Ministry of Education, PR China

Received: 17 May 2013
Accepted: 26 July 2013

Abstract

Context. Chromospheric evaporation is a key process in solar flares that has been extensively investigated using spectroscopic observations. However, direct soft X-ray (SXR) imaging of the process is rare, especially in remote brightenings associated with the primary flares that have recently attracted a great deal of attention.

Aims. We intend to find the evidence for chromospheric evaporation and figure out the cause of the process in sympathetic coronal bright points (CBPs), i.e., remote brightenings induced by the primary CBP.

Methods. We utilised the high-cadence and high-resolution SXR observations of CBPs from the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 23.

Results. We discovered a thermal conduction front propagating from the primary CBP (hereafter BP1) to the first of the sympathetic CBPs (hereafter BP2) that is 60″ away from BP1. The apparent velocity of the thermal conduction is ~138 km s^-1. Afterwards, hot plasma flowed upwards into the loop connecting BP1 and BP2 at a speed of ~76 km s^-1, a clear signature of chromospheric evaporation. Similar upflow was also observed in the loop connecting BP1 and the other sympathetic CBP (hereafter BP3) that is 80″ away from BP1, though less significant than BP2. The apparent velocity of the upflow is ~47 km s^-1. The thermal conduction front propagating from BP1 to BP3 was not well identified except for the jet-like motion also originating from BP1.

Conclusions. We propose that the gentle chromospheric evaporation in the sympathetic CBPs were caused by thermal conduction originating from the primary CBP.