彗星21 P/Giacobini-Zinner：与SOHO/SWAN合作20年的水生产活动
Comet 21P/Giacobini-Zinner: Water Production Activity over 20 Years with SOHO/SWAN
摘要：
1985年，21 P/Giacobini-Zinner彗星是第一颗被国际彗星探测器（ICE）探测到的彗星，比1986年的哈雷彗星探测器早了几个月。ICE最初是ISEE-3卫星，设计用于地球附近的磁层测量，并通过月球重力辅助转向穿过彗星的等离子体尾部。这颗彗星在1998年，2005年，2012年和2018年的最后四次出现期间被太阳和日光层观测卫星上的全天空氢莱曼α太阳风各向异性（SWAN）相机观测到。本文比较了Combi等人（2011年）发表的1998年和2005年氢图像计算的产水率，以及2012年和2018年的新观测结果。与一些随着时间推移而褪色的彗星不同，除了2012年的结果中看到的两次爆发外，彗星21 P的活动水平并没有随着时间的推移而发生一致的变化。对所有四次出现的近日点前的产水率与日心距离进行幂律拟合，得到的结果为3.75 x 10^28 x r^-0.28+/-0.4，而对近日点后的产水率，扣除2012年以爆发为主的数据，得到的结果为4.15 x 10^28 x r^-10.2+/-0.9。产生率以s^-1为单位，日心距离以AU为单位。
英文摘要：
In 1985 Comet 21P/Giacobini-Zinner was the first comet visited by a spacecraft, the International Cometary Explorer (ICE) satellite, several months before the armada of Halley spacecraft had their encounters in 1986. ICE was originally the ISEE-3 satellite, designed for magnetospheric measurements near the Earth, and was diverted via a lunar gravity assist to pass through the plasma tail of the comet. The comet has been observed by the all-sky hydrogen Lyman-alpha Solar Wind Anisotropies (SWAN) camera on the SOlar and Heliospheric Observatory satellite during its last four apparitions in 1998, 2005, 2012 and 2018. This paper compares water production rates calculated from the hydrogen images from the 1998 and 2005 results, published by Combi et al. (2011), with new observations from 2012 and 2018. Unlike some comets that have faded over time, except for 2 outbursts seen in the 2012 results, the activity levels for Comet 21P have not changed consistently over time. A power-law fit to the pre-perihelion water production rate vs. heliocentric distance for all four apparitions gives a result of 3.75x10^28 x r^-0.28+/-0.4, and that for the post-perihelion production rate, discounting 2012 data dominated by outbursts, gives 4.15 x 10^28 x r^-10.2+/-0.9. The production rates are in s^-1 and heliocentric distances are in AU.
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