CHANGES IN THE PHYSICAL ENVIRONMENT OF THE INNER COMA OF 67P/CHURYUMOV-GERASIMENKO WITH DECREASING HELIOCENTRIC DISTANCE
CHANGES IN THE PHYSICAL ENVIRONMENT OF THE INNER COMA OF 67P/CHURYUMOV-GERASIMENKO WITH DECREASING HELIOCENTRIC DISTANCE
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DOI：
10.3847/0004-6256/152/5/130
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发表时间：
2016-11-01
影响因子：
5.3
通讯作者：
Vincent, J. -B.
中科院分区：
文献类型：
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作者：
Bodewits, D.;Lara, L. M.;Vincent, J. -B.
罗塞塔号航天器上的OSIRIS仪器的广角相机配备了几个窄带滤光片，这些滤光片以各种碎片物种的发射线和带为中心。它们被用来确定67P彗星内部彗发中气体的产生和空间分布随时间和日心距离的演变，这里是2.6到1.3Au的近日点前。我们的观察表明，在OH、OI、CN、NH和NH2滤光片中观察到的发射主要是由不同母体的离解电子碰撞激发产生的。我们得出结论，CO2而不是H2O是[OI]630 nm发射的重要来源。在CN和OI滤光片中观察到的一个强烈的羽状特征贯穿于我们的整个观测过程。这一羽状物不存在于OH发射中，表明局部CO2/H2O比增加了3倍。我们在2015年3月之后观察到强度水平突然下降，我们将其归因于原子核表面上方最初几公里的电子温度下降。
The Wide Angle Camera of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrow-band filters that are centered on the emission lines and bands of various fragment species. These are used to determine the evolution of the production and spatial distribution of the gas in the inner coma of comet 67P with time and heliocentric distance, here between 2.6 and 1.3 au pre-perihelion. Our observations indicate that the emission observed in the OH, OI, CN, NH, and NH2 filters is mostly produced by dissociative electron impact excitation of different parent species. We conclude that CO2 rather than H2O is a significant source of the [OI] 630 nm emission. A strong plume-like feature observed in the CN and OI filters is present throughout our observations. This plume is not present in OH emission and indicates a local enhancement of the CO2/H2O ratio by as much as a factor of 3. We observed a sudden decrease in intensity levels after 2015 March, which we attribute to decreased electron temperatures in the first few kilometers above the surface of the nucleus.