Variable morphology of Saturn's southern ultraviolet aurora
Variable morphology of Saturn's southern ultraviolet aurora
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土星南紫外极光的可变形态
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
J. Clarke
中科院分区：
文献类型：
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作者：
D. Grodent;J. Gérard;S. Cowley;E. Bunce;J. Clarke
[1]哈勃太空望远镜上的太空望远镜成像光谱仪相机在2004年1月8日至30日期间获得了68张土星南部极光发射的FUV图像，卡西尼号接近土星的磁层。HST观测发生在四个不同的太阳风区域，1月8日至16日为低场稀疏区，1月17日为轻微压缩事件，1月19日至25日为中等场强的稀疏区，1月26日至30日为主要压缩区。这些图像已被投影到极地地图上，以便描述和比较极光发射的一般形态。前20张照片是在土星一次完整旋转的70%期间拍摄的。他们表明，明亮的极光发射环实际上是由几个不同宽度和亮度的弧组成，并沿着不同的平行线形成。总体而言，极光区的旋转速度是整个行星旋转的65%，尽管一些孤立的极光结构的角速度随着时间的推移不断下降，下降到20%。极光降水最强出现在早晨。其余48幅图像的极投影证实了形态的巨大变化，其特征在于不同的平均区域。在运动期间，短暂的时间间隔，在此期间，极光区显着收缩，并清楚地形成一个螺旋，其次是极光区的再膨胀的间隔。这表明，这两次主要的极光收缩事件对应于卡西尼号在1月17日和1月25日观测到的太阳风冲击的到来。目前的分析表明，土星的极光形态响应于土星的太阳风条件。
[1] The Space Telescope Imaging Spectrograph camera on board Hubble Space Telescope obtained 68 FUV images of Saturn's southern auroral emission between 8 and 30 January 2004, during Cassini's approach to Saturn's magnetosphere. The HST observations took place in four different solar wind regimes with a low-field rarefaction region from 8 to 16 January, a minor compression event on 17 January, a rarefaction region with intermediate field strengths from 19 to 25 January, and a major compression region from 26 to 30 January. The images have been projected onto polar maps in order to characterize and compare the general morphology of the auroral emission. The first 20 images were obtained during a period covering about 70% of one full rotation of Saturn. They show that the bright ring of auroral emission actually consists of several arcs of different width and brightness and forming along different parallels. Overall, the auroral region is shown to rotate at ∼65% of the full planetary rotation, although the angular velocity of some isolated auroral structures constantly decrease with time, down to 20%. The strongest auroral precipitations are observed in the morning sector. The polar projections of the 48 remaining images confirm dramatic changes in morphology, characterized by different average zones. During the campaign, short intervals during which the auroral region is significantly contracted and clearly forms a spiral were followed by intervals of reinflation of the auroral region. It is suggested that the two major auroral contraction events corresponded to the arrival of the solar wind shocks observed by Cassini on 17 January and 25 January. The present analysis indicates that Saturn's auroral morphology responds to the solar wind conditions at Saturn.