Saturn's magnetodisc current sheet
Saturn's magnetodisc current sheet
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DOI：
10.1029/2007ja012540
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发表时间：
2008-04
期刊：
影响因子：
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通讯作者：
C. Arridge;C. Russell;N. Achilleos;K. Khurana;M. Dougherty;S. Cowley;E. Bunce;D. Southwood
中科院分区：
文献类型：
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作者：
C. Arridge;C. Russell;N. Achilleos;K. Khurana;M. Dougherty;S. Cowley;E. Bunce;D. Southwood
[1]先驱者11号在土星磁层黎明侧的观测为薄赤道电流片提供了证据。来自卡西尼号轨道器的磁力计数据也揭示了这个电流片的存在，并表明它是黎明侧翼的一致特征。Arridge等人（2007）最近研究了这个电流片中的应力平衡，并表明离心力在距离土星20 - 30 RS的径向距离之外占主导地位。这些观测结果使Arridge等人（2007年）将这一电流片解释为一个磁盘，类似于木星磁层中的磁盘，但在当地时间中强烈不对称。在本文中，我们提出了一个调查，这些薄电流片在土星的磁层，并表明，他们已被观察到在所有当地时间卡西尼号探索外磁层超过15 RS。我们将这些观测结果解释为土星磁盘电流片的证据，并表明在某些条件下，磁盘并不像Arridge等人（2007）首次提出的那样不对称。在太阳风动力压力较低的情况下，即太阳下磁层顶距离大于23 RS时，土星环电流会主导土星内部磁场，并产生一个磁盘。在压缩下，昼侧磁场变得更加偶极，磁盘只存在于磁层的夜侧和侧翼。因此，与木星的磁盘不同，克罗尼亚磁盘对上游的太阳风条件非常敏感。我们还提出了理论应力平衡计算支持在土星，在那里我们表明，离心力的存在是足够的，以产生所观察到的磁盘。
[1] Pioneer 11 observations from the dawn flank of Saturn's magnetosphere provided evidence for a thin equatorial current sheet. Magnetometer data from the Cassini orbiter have also revealed the presence of this current sheet and shown it to be a consistent feature of the dawn flank. Arridge et al. (2007) recently investigated the stress balance in this current sheet and showed that the centrifugal force dominated the mechanical stresses beyond a radial distance of 20–30 RS from Saturn. These observations led Arridge et al. (2007) to interpret this current sheet as a magnetodisc, similar to that in the jovian magnetosphere but strongly asymmetric in local time. In this paper we present a survey of these thin current sheets in Saturn's magnetosphere and show that they have been observed at all local times where Cassini has explored the outer magnetosphere beyond 15 RS. We interpret the observations as evidence for Saturn's magnetodisc current sheet and show that under certain conditions the magnetodisc is not as asymmetric as Arridge et al. (2007) first suggested. Under low solar wind dynamic pressures where the subsolar magnetopause standoff distance is >23 RS, Saturn's ring current dominates over Saturn's internal field and produces a magnetodisc. Under compression the dayside field becomes more dipolar and the magnetodisc is only present on the nightside and flanks of the magnetosphere. Hence in contrast to Jupiter's magnetodisc, the kronian magnetodisc is highly sensitive to the upstream solar wind conditions. We also present theoretical stress balance calculations supporting the existence of a magnetodisc at Saturn, where we show that the centrifugal force is plausibly sufficient to produce the observed magnetodisc.