Discovery of Accelerating Plasmoids in the Tail of Comet Encke
Abstract
Comet 2P/Encke was the second comet to have its return correctly predicted (in 1819). Encke is a Jupiter-family comet with a period of 3.30 years and a perihelion distance of 0.338 AU. The interaction between cometary plasma and the solar wind plasma provides the potential for remote monitoring of the solar wind. In this regard comet Encke is potentially a very useful probe of the solar wind because of its very short orbital period and therefore large number of close approaches to the Sun. However, for this reason it is likely to have exhausted most of its reserves of ice and therefore possess a less dense plasma tail. The comet could therefore respond faster and more dynamically to solar wind variations than the tail of a more active or higher gas production comet. The Heliospheric Imager (HI) of STEREO-A (HI-1A), observed comet 2P/Encke during April, 2007. The comet was predicted to have reached perihelion on April 19th 0 UT. This paper will only consider the observations obtained by HI-1A on April 25th to 27th, 2007. At this time the comet was around 0.63 AU from Earth and 0.39 AU from the Sun. The comet was seen to exhibit a distinct "flick" of its plasma tail on April 26th and a series of "whiplash" events. However, the most interest phenomena seen was a whole series of "plasmoids" that were observed to break off from the brighter part of the tail near the nucleus and accelerate along the tail for 4-5 million kilometres down-wind of the nucleus.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMSH33A1087K
- Keywords:
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- 6025 Interactions with solar wind plasma and fields;
- 6050 Plasma and MHD instabilities (2149;
- 2752;
- 7836);
- 6210 Comets (6023);
- 7811 Discontinuities (2109);
- 7846 Plasma energization