Magnetotail reconnection rate during magnetospheric substorms
Magnetotail reconnection rate during magnetospheric substorms
复制标题
磁层亚暴期间磁尾重联率
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
O. Beaujardiere
中科院分区：
文献类型：
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作者：
G. Blanchard;L. Lyons;O. Beaujardiere
利用Sondrestrom非相干散射雷达在24个亚暴的集合期间采集的数据研究了亚暴期间的磁尾重联率。一个叠加的历元分析表明，磁尾重联增加略显着高于其平均水平的亚暴扩张阶段开始的时间附近。我们的数据集显示，在发病±5分钟内，这种增加的置信度为87%，在发病后10± 5分钟，置信度大于99%。然而，中位重连率测量值直到发作后20分钟才开始增加。这种效应是由于亚暴期间磁尾重连发展的空间变化;磁尾重连在午夜附近的一个小的磁性当地时间扇区发病后很快增加，而在大多数分界线，重连率的增加被推迟。在当地时间部门大于1.5小时，从午夜的平均延迟约为20分钟。我们分配功能形式的磁尾重联率的平均依赖于磁当地时间，行星际磁场，和亚暴活动，并分析这些功能的广义线性组合。得到的表达式由平均行星际磁场和亚暴依赖的重联率的平均空间变化的总和组成，并占重联率方差的36%（0.55线性相关），这是低频（f <0.5h-1）变化的主要部分。重连率的剩余方差主要是噪声，其水平与重连率测量不确定性一致。
The magnetotail reconnection rate during substorms is studied using data taken by the Sondrestrom incoherent scatter radar during an ensemble of 24 substorms. A superposed epoch analysis indicates that magnetotail reconnection increases marginally significantly above its average level near the time of substorm expansion phase onset. Our data set shows this increase with 87% confidence within ±5 min of onset and with greater than 99% confidence at 10± 5 min after onset. However, the median reconnection rate measurement does not begin to increase until 20 min after onset. This effect is shown to be due to a spatial variation in the development of magnetotail reconnection during substorms; magnetotail reconnection increases very soon after onset in a small magnetic local time sector near midnight, while over most of the separatrix, the increase in the reconnection rate is delayed. The average delay in the local time sectors greater that 1.5 hours from midnight is approximately 20 min. We assign functional forms to the average dependence of the magnetotail reconnection rate on magnetic local time, on the interplanetary magnetic field, and on substorm activity, and analyze the generalized linear combination of these functions. The resulting expression consists of the sum of the average interplanetary magnetic field and substorm dependence of the reconnection rate gated by the average spatial variation and accounts for 36% of the variance in the reconnection rate (0.55 linear correlation), which is most of the low-frequency (f < 0.5 h -1 ) variation. The residual variance in the reconnection rate is mostly noise at a level consistent with the reconnection rate measurement uncertainty.