Characterization of auroral current systems in Saturn's magnetosphere: High-latitude Cassini observations
Characterization of auroral current systems in Saturn's magnetosphere: High-latitude Cassini observations
复制标题
土星磁层极光电流系统的特征：高纬度卡西尼号观测
DOI：
--
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
M. Dougherty
中科院分区：
文献类型：
--
作者：
C. Arridge;A. Coates;D. Talboys;E. Bunce;S. Cowley;M. Dougherty
[1]在卡西尼号飞行任务的第一个高纬度阶段，从2006年年中到2007年年中，我们已经确定了七次近地点飞行，航天器在中等高度穿越了最高纬度的开放场线之间的区域和环流内边缘内的区域。在所有这些通道上，在两个半球都观察到了不同的方位磁场，表明存在场向电流，对应于夏季南半球的黎明和前夜扇区，以及冬季北半球的黄昏到午夜前扇区。在南半球，观察到在开放场线上观测到的强“滞后”场在开闭场线边界上迅速下降，然后通常在封闭场线的窄层中从意义上逆转为“领先”配置，然后下降到由内部区域行星周期振荡的相位决定的较小值。这些观测表明，该区域的等离子体流从开放场线上的次公转急剧增加到闭合场线上的超余旋层，并伴随着一层向上定向的场向电流，这一层显示出与南极光椭圆形的统计位置相同。随着引导场的减弱，向下的电流随后在内部区域流动。然而，在北半球，在开放场线上只观察到微弱的方位向场，这表明如果等离子体类似地次共转，则冬季电离层的导电性很弱，而在封闭场区，立即观察到一层更强的滞后场，表明次共转。因此，在这种情况下，磁场对准的电流正好在边界内向下引导，在与南半球相反的内部区域向上引导，但再次受到两侧行星周期振荡的场的调制。
[1] We have identified seven periapsis passes during the first high-latitude phase of the Cassini mission, from mid-2006 to mid-2007, in which the spacecraft traversed at intermediate altitudes the region between open field lines at highest latitudes and the region inside the inner edge of the ring current. Varying azimuthal magnetic fields indicative of the presence of field-aligned currents were observed in both hemispheres on all these passes, corresponding to the dawn and prenoon sector in the summer southern hemisphere and the dusk to premidnight sector in the winter northern hemisphere. In the southern hemisphere, strongly “lagging” fields observed on open field lines are observed to decline rapidly across the open-closed field line boundary, usually then reversing in sense to a “leading” configuration in a narrow layer of closed field lines, before declining to smaller values determined by the phase of the planetary period oscillation in the inner region. These observations suggest that the plasma flow in this sector increases sharply across the boundary from subcorotation on open field lines to a layer of supercorotation on closed field lines, accompanied by a major layer of upward-directed field-aligned current that is shown to be colocated with the statistical location of the southern auroral oval. Downward current then flows in the inner region as the leading field declines. In the northern hemisphere, however, only weak azimuthal fields are observed on open field lines, suggesting weak conductivity in the winter ionosphere if the plasma similarly subcorotates, while a layer of stronger lagging field indicative of subcorotation is observed immediately equatorward in the closed field region. The field-aligned currents in this case are thus directed downward just inside the boundary and upward in the interior region, opposite to the southern hemisphere, but are again modulated by the field of the planetary period oscillations on either side.
DOI：
10.1029/2008ja013257
发表时间：
2008-09
期刊：
Scopus
影响因子：
--
作者：
E. Bunce;C. Arridge;J. Clarke;A. Coates;S. Cowley;M. Dougherty;Jean-Claude Gérard;D. Grodent;K. Hansen;J. Nichols;D. Southwood;D. Southwood;D. Talboys
通讯作者：
E. Bunce;C. Arridge;J. Clarke;A. Coates;S. Cowley;M. Dougherty;Jean-Claude Gérard;D. Grodent;K. Hansen;J. Nichols;D. Southwood;D. Southwood;D. Talboys
土星白天磁层的磁场结构及其到电离层的映射：环流模型的结果
DOI：
10.1029/2007ja012538
发表时间：
2008
期刊：
Space Physics
影响因子：
--
作者：
Bunce E
通讯作者：
Bunce E
土星磁层中的行星周期振荡：赤道磁场振荡与土星千米辐射调制的相位关系
DOI：
10.1029/2007ja012937
发表时间：
2008
期刊：
Space Physics
影响因子：
--
作者：
Andrews D
通讯作者：
Andrews D