Mercury's magnetosphere after MESSENGER's first flyby
Mercury's magnetosphere after MESSENGER's first flyby
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DOI：
10.1126/science.1159040
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发表时间：
2008-07-04
期刊：
影响因子：
56.9
通讯作者：
Zurbuchen, Thomas H.
中科院分区：
文献类型：
--
作者：
Slavin, James A.;Acuna, Mario H.;Zurbuchen, Thomas H.
信使号的观测显示，水星的磁层浸没在一个类似彗星的行星离子云中。最丰富的Na+分布广泛，但在磁鞘中表现出最大的通量，在那里局部等离子体流动速度高，靠近航天器最接近的地方，大气密度应该达到峰值。磁场以通量转移事件、沿磁层顶与开尔文-亥姆霍兹波一致的方位旋转和广泛的超低频波活动的形式表现出重联特征。观察到两个输出电流片边界，在其上磁场以双磁层顶的方式减弱。这些电流层的分离，相当于在磁鞘中加速后进入磁层的Na+拾取离子的陀螺半径，可能表明存在行星离子边界层。
Observations by MESSENGER show that Mercury's magnetosphere is immersed in a comet- like cloud of planetary ions. The most abundant, Na+, is broadly distributed but exhibits flux maxima in the magnetosheath, where the local plasma flow speed is high, and near the spacecraft's closest approach, where atmospheric density should peak. The magnetic field showed reconnection signatures in the form of flux transfer events, azimuthal rotations consistent with Kelvin- Helmholtz waves along the magnetopause, and extensive ultralow- frequency wave activity. Two outbound current sheet boundaries were observed, across which the magnetic field decreased in a manner suggestive of a double magnetopause. The separation of these current layers, comparable to the gyro- radius of a Na+ pickup ion entering the magnetosphere after being accelerated in the magnetosheath, may indicate a planetary ion boundary layer.