Cassini observations of ion and electron beams at Saturn and their relationship to infrared auroral arcs
Cassini observations of ion and electron beams at Saturn and their relationship to infrared auroral arcs
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DOI：
10.1029/2011ja017222
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发表时间：
2012-01-21
影响因子：
2.8
通讯作者：
Tao, C.
中科院分区：
文献类型：
--
作者：
Badman, S. V.;Achilleos, N.;Tao, C.
我们目前卡西尼视觉和红外测绘光谱仪观测的红外极光发射从中午部门的土星的电离层揭示多个强烈的极光弧分离的黑暗地区的主要椭圆极向。弧被解释为发生在昼侧磁层顶的重联爆发的电离层签名。极光弧与向上的场向电流有关，卡西尼号在行星高纬度地区探测到了磁场特征。在邻近的向下电流区域的磁场和粒子观测显示，除了高能（数百keV）电子外，还有100-360 keV的轻离子向上爆发，这些电子可能是从携带向下电流的向上加速束散射的。宽带，向上传播的哨声波同时检测到的离子束。来自低空的轻离子的加速归因于向下流区的波粒相互作用。高能（600千电子伏）的氧离子也被检测到，这表明在加速区域内的海拔高度的环境氧气的存在。这些同时进行的现场和远程观测揭示了驱动土星一些不寻常的极光特征的高能量磁层动力学。这是第一次在现场识别的瞬态重连事件在磁共轭的区域土星的磁层顶。
We present Cassini Visual and Infrared Mapping Spectrometer observations of infrared auroral emissions from the noon sector of Saturn's ionosphere revealing multiple intense auroral arcs separated by dark regions poleward of the main oval. The arcs are interpreted as the ionospheric signatures of bursts of reconnection occurring at the dayside magnetopause. The auroral arcs were associated with upward field-aligned currents, the magnetic signatures of which were detected by Cassini at high planetary latitudes. Magnetic field and particle observations in the adjacent downward current regions showed upward bursts of 100-360 keV light ions in addition to energetic (hundreds of keV) electrons, which may have been scattered from upward accelerated beams carrying the downward currents. Broadband, upward propagating whistler waves were detected simultaneously with the ion beams. The acceleration of the light ions from low altitudes is attributed to wave-particle interactions in the downward current regions. Energetic (600 keV) oxygen ions were also detected, suggesting the presence of ambient oxygen at altitudes within the acceleration region. These simultaneous in situ and remote observations reveal the highly energetic magnetospheric dynamics driving some of Saturn's unusual auroral features. This is the first in situ identification of transient reconnection events at regions magnetically conjugate to Saturn's magnetopause.