Magnetic flux circulation in the rotationally driven giant magnetospheres
Magnetic flux circulation in the rotationally driven giant magnetospheres
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DOI：
10.1002/2015ja021036
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发表时间：
2014-12
期刊：
影响因子：
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通讯作者：
P. Delamere;A. Otto;Xuanye Ma;F. Bagenal;R. Wilson
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文献类型：
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作者：
P. Delamere;A. Otto;Xuanye Ma;F. Bagenal;R. Wilson
巨行星磁盘是由源自内部磁层的等离子体的径向传输形成的。磁通量传输是磁盘拉伸磁场配置的一个关键方面。虽然净质量传输是向外的(最终失去了太阳风)，但磁通量守恒需要一个平衡的双向传输过程。磁重联是平衡磁通输运的一个重要方面。我们利用2004年至2012年的卡西尼磁力仪数据，对土星磁层的电流片交叉进行了全面的分析，试图量化磁通量的循环，强调与当地时间的相关性。磁通传输的一个关键特性是磁场的方位向前弯曲或向后弯曲。回弯构形是净质量流出的磁盘的预期特性，但由于重联后大部分空通量管的快速内移，可以实现正向折弯构形。我们发现弯折正向情形具有很强的局地时间依赖性，主要集中在午后区域，这表明通量守恒的重联大部分发生在次太阳和黄昏区域。我们认为，重新连接发生在一个复杂而零星的重新连接地点网络中，这支持了等离子体可以通过“毛毛雨”般的过程在小范围内丢失的观点。还将介绍观测到的通量环流的极光含义。
The giant‐planet magnetodiscs are shaped by the radial transport of plasma originating in the inner magnetosphere. Magnetic flux transport is a key aspect of the stretched magnetic field configuration of the magnetodisc. While net mass transport is outward (ultimately lost to the solar wind), magnetic flux conservation requires a balanced two‐way transport process. Magnetic reconnection is a critical aspect of the balanced flux transport. We present a comprehensive analysis of current sheet crossings in Saturn's magnetosphere using Cassini magnetometer data from 2004 to 2012 in an attempt to quantify the circulation of magnetic flux, emphasizing local time dependence. A key property of flux transport is the azimuthal bend forward or bend back of the magnetic field. The bend back configuration is an expected property of the magnetodisc with net mass outflow, but the bend forward configuration can be achieved with the rapid inward motion of mostly empty flux tubes following reconnection. We find a strong local time dependence for the bend forward cases, localized mostly in the postnoon sector, indicating that much of the flux‐conserving reconnection occurs in the subsolar and dusk sector. We suggest that the reconnection occur in a complex and patchy network of reconnection sites, supporting the idea that plasma can be lost on small scales through a “drizzle”‐like process. Auroral implications for the observed flux circulation will also be presented.