鹿林彗星的断尾事件研究

The Disconnection Event of Comet Lulin

鹿林彗星在2009年2月4日(UT)发生了一次断尾事件,通过对2月4日前后的观测数据进行分析,发现在2月3日鹿林彗星就已发生过一次断尾事件.对2月3日发生的断尾事件进行研究可得出断尾移动的速度为68 km·s^(-1),断尾事件发生的时间为2009年2月3日(15.24±5.16)时.结合断尾事件发生前后鹿林彗星的轨道特征和STEREO-A飞船所测量到的太阳风数据,鹿林彗星2月3日发生的断尾事件可能是由于日冕物质抛射和彗星相互作用导致的磁重联引起的.

The disconnection event （DE） is the entire plasma tail or its part separates from the cometary head. It is one of the most spectacular phenomena of comets. The driving mechanism remained unresolved and there are many competitive theories to explain the onset of DE at present. However, the variable solar wind is suspected to play a major role. Comet Lulin showed a DE on 2009 February 4. The data around this day are analyzed and it is found that comet Lulin had already occurred a DE on 2009 February 3. By comparing the morphology of plasma tail of these two DEs, it is concluded that the DE occurred on 2009 February 3 is a new DE, different from that occurred on 2009 February 4. In this paper, we report the result of the analysis of DE on 2009 February 3. The calculated occurrence time of DE is, in UT decimal date, 2009 February 3.635 ±0.215. The radial velocity of the disconnection tail is about 68 km.s^-1. Considering the orbit characters of comet Lulin and the solar wind conditions around comet Lulin, it is concluded that the DE occurred on 2009 February 3 was driven by magnetic reconnection between comet and a coronal mass ejection. The solar wind conditions around comet Lulin are inferred to the comet by corotation of STEREO-A data.