Geomagnetic signatures of auroral substorms preceded by pseudobreakups
Geomagnetic signatures of auroral substorms preceded by pseudobreakups
复制标题
假分裂之前的极光亚暴的地磁特征
DOI：
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发表时间：
2009
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通讯作者：
T. Karlsson
中科院分区：
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作者：
A. Kullen;S. Ohtani;T. Karlsson
1998-1999年冬季期间，在北方半球极地紫外线图像中确定的10个生长阶段伪破裂和随后的亚暴的演变与AE指数、统一PC指数和GOES B场数据进行了比较。将亚暴爆发（极光分裂）与GOES数据以及AE和PC指数进行比较，发现在大多数情况下不可能根据这些参数准确确定爆发。三个最弱的亚暴在辅助参数中没有留下明显的特征。对于其他事件，AE增加出现在发作后5-15分钟的时间延迟。正如预期的那样，PC指数在AE指数之前增加。PC增加和发作之间的时间跨度变化很大（-26至5分钟）。在GOES数据中观察到尾双极化，发作后延迟2-31分钟。地球同步轨道上的偶极延迟是由于GOES从尾始区的位移引起的。利用GOES距极光破裂区的距离作为GOES距破裂源区位移的估计值，我们发现尾偶极区平均以0.22 MLT min（-1）的方位角速度和0.09度min（-1）的赤道速度扩展。除了在四个最强的亚暴情况下，伪破裂几乎没有留下任何AE或PC指数数据的签名。在这些情况下，在伪破裂期间，PC指数中出现凸起。地球同步B场数据中的一个凸起仅在GOES位于非常接近伪破裂尾源区的这两种情况下被发现。
The evolution of ten growth-phase pseudobreakups and subsequent substorms, identified in Northern Hemisphere Polar UV images during winter 1998-1999, are compared to the AE index, the unified PC indices, and GOES B field data. Comparing substorm onset (auroral breakup) with GOES data and AE and PC indices, it is found that an exact onset determination from these parameters is in most cases not possible. The three weakest substorms leave no clear signatures in the auxiliary parameters. For the other events, the AE increase appears with a time delay of 5-15 min after onset. The PC indices increase, as expected, before the AE index. The time span between PC increase and onset varies widely (-26 to 5 min). A tail dipolarization is seen in GOES data with a time delay of 2-31 min after onset. The dipolarization delay at geosynchronous orbit appears because of the GOES displacement from the tail onset region. Using the mapped GOES distance from the auroral breakup region as an estimate of GOES displacement from the breakup source region, we find that the tail dipolarization region expands in average with an azimuthal speed of 0.22 MLT min(-1) and an equatorward speed of 0.09 degrees min(-1). Pseudobreakups leave hardly any signature in AE or PC index data except in the four strongest substorm cases. In these cases, a bump appears in the PC indices during the pseudobreakup. A bump in geosynchronous B field data is found only in those two cases where GOES is located very close to the pseudobreakup tail source region.