Interplanetary conditions and magnetospheric dynamics during the Cassini orbit insertion fly-through of Saturn's magnetosphere
Interplanetary conditions and magnetospheric dynamics during the Cassini orbit insertion fly-through of Saturn's magnetosphere
复制标题
卡西尼轨道插入飞越土星磁层期间的行星际条件和磁层动力学
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
P. Zarka
中科院分区：
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作者：
C. Jackman;N. Achilleos;E. Bunce;B. Cecconi;J. Clarke;S. Cowley;W. Kurth;P. Zarka
[1]本文的主要目的是讨论行星际的条件下，在土星轨道插入（SOI）飞越土星的磁层的卡西尼号航天器在2004年6月至7月和随之而来的磁层动力学。我们开始检查并发行星际磁场（IMF）和土星公里辐射（SKR）数据从卡西尼号与图像从哈勃太空望远镜（HST）从2004年1月的间隔，这表明在土星的共转相互作用区域（CIR）相关的压缩区域的到来的影响。然后，我们研究了国际货币基金组织的数据获得了五个太阳旋转包围SOI飞通过，并表明，一个类似的CIR压缩和嵌入式交叉的日光层电流片（HCS）预计有冲击土星的磁层在某个时候在飞通过。检查飞行通道两侧的IMF方向，确认HCS过境点。SKR的观测结果表明，相对较弱的排放调制在行星自转周期的SOI入境通行证。在出站通道上观察到了延伸到低频的强爆发，这些爆发与之前的发射不同步，类似于1月份数据中看到的与CIR相关的SKR爆发。因此，我们认为，入境通行证发生在未压缩的条件下的SKR和极光安静，而大部分的出境通行证发生在压缩条件下的SKR和极光干扰，可能是相同的一般性质，观察到与CIR压缩在2004年1月的HST卡西尼号活动。我们还研究了卡西尼号在黎明前扇区观测到的原位磁场数据，发现最大的发射爆发与黎明前磁场的并发变化有关，这表明航天器上注入了热等离子体。具体地，在初始场强增加之后，场的强度降低并且随时间高度可变。这些意见是一致的注入到夜侧磁层的热等离子体的尾巴，我们建议连接到极光过程中观察到的HST在2004年1月的运动相同的性质。注入可能与压缩引起的尾部重连有关，因为已经提出解释在HST卡西尼号活动数据中观察到的极光特征。
[1] The primary purpose of this paper is to discuss the interplanetary conditions that prevailed during the Saturn orbit insertion (SOI) fly-through of Saturn's magnetosphere by the Cassini spacecraft in June–July 2004 and the consequent magnetospheric dynamics. We begin by examining concurrent interplanetary magnetic field (IMF) and Saturn kilometric radiation (SKR) data from Cassini together with images from the Hubble Space Telescope (HST) from an interval in January 2004, which show the effect of the arrival at Saturn of a corotating interaction region (CIR)-related compression region. We then examine the IMF data obtained over five solar rotations bracketing the SOI fly-through and show that a similar CIR compression and embedded crossing of the heliospheric current sheet (HCS) is expected to have impinged on Saturn's magnetosphere at some time during the fly-through. Examination of the IMF direction on either side of the fly-through confirms the HCS crossing. Observations of SKR show relatively weak emissions modulated at the planetary rotation period on the SOI inbound pass. Strong bursts extending to low frequencies, which are not in phase with the previous emissions, were observed on the outbound pass, similar to the CIR-related SKR bursts seen in the January data. We thus suggest that the inbound pass occurred under uncompressed conditions of SKR and auroral quiet, while much of the outbound pass occurred under compressed conditions of SKR and auroral disturbance, probably of the same general character as observed in association with CIR compressions during the HST-Cassini campaign in January 2004. We also examine the in situ magnetic field data observed outbound by Cassini in the predawn sector and find that the largest emission bursts are associated with concurrent variations in the predawn magnetic field, which are indicative of the injection of hot plasma at the spacecraft. Specifically, after an initial field strength increase, the field becomes depressed in strength and highly variable in time. These observations are consistent with an injection of hot plasma into the nightside magnetosphere from the tail, which we suggest is connected with auroral processes of the same nature as observed by the HST during the January 2004 campaign. The injection may be associated with compression-induced reconnection in the tail, as has been proposed to explain the auroral signatures observed in the HST-Cassini campaign data.