A New Empirical Model of the Subauroral Polarization Stream
A New Empirical Model of the Subauroral Polarization Stream
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DOI：
10.1029/2018ja025690
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发表时间：
2018-09
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通讯作者：
B. Kunduri;J. Baker;J. Ruohoniemi;N. Nishitani;K. Oksavik;P. J. Erickson;A. Coster;S. Shepherd;W. Bristow;E. S. Miller
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作者：
B. Kunduri;J. Baker;J. Ruohoniemi;N. Nishitani;K. Oksavik;P. J. Erickson;A. Coster;S. Shepherd;W. Bristow;E. S. Miller
在黄昏-午夜扇区，在极光椭圆的赤道方向经常观测到持续向西流动的区域。一般来说，午夜窄流称为亚极光离子漂移，而黄昏宽流称为亚极光极化流（SAPS）。SAPS/亚极光离子漂移电场在控制中纬度电离层动力学中起着重要作用。本文分析了不同地磁条件下中纬度超双极光雷达网（SuperDARN）雷达测量的SAPS纵向扩展观测结果。我们发现SAPS速度对地磁活动有很强的依赖性，在地磁风暴期间流量超过1500 m/s，在地磁平静期间下降到100 m/s。此外，当从午夜扇区向黄昏移动时，SAPS流越来越向极地移动，这种影响在地磁扰动条件下更为明显。SAPS速度随磁地方时（MLT）的变化也被发现强烈依赖于地磁条件。具体来说，在受干扰的地磁条件下，SAPS速度随MLT呈拟线性增加，而在相对安静的地磁条件下，SAPS速度没有明显的趋势。这种行为表明在地磁安静条件下影响SAPS的不同机制的可能性。平均交叉- SAPS电位随着地磁活动的增加而增加，通常在15至45千伏之间变化。最后，建立了一个新的SAPS电位的经验模型，该模型由Asy - H指数、MLT和磁纬度参数化。
Regions of persistent westward directed flows are often observed equatorward of the auroral oval in the dusk‐midnight sector. In general, the midnight narrow flows are termed as subauroral ion drifts and the duskside broader flows are termed subauroral polarization streams (SAPS). SAPS/subauroral ion drift electric fields play an important role in controlling the dynamics of the midlatitude ionosphere. In this paper we analyze longitudinally extended observations of SAPS measured by midlatitude Super Dual Auroral Radar Network (SuperDARN) radars under varied geomagnetic conditions. We find that SAPS speeds exhibit a strong dependence on geomagnetic activity, with flows exceeding 1,500 m/s during geomagnetic storms and dropping to 100 m/s during periods of geomagnetic quiet. Moreover, SAPS flows turn increasingly poleward when moving from the midnight sector toward dusk and this effect is more pronounced during disturbed geomagnetic conditions. The variations in SAPS speeds with magnetic local time (MLT) are also found to be strongly dependent on geomagnetic conditions. Specifically, SAPS speeds increase quasilinearly with MLT during disturbed geomagnetic conditions, whereas during relatively quiet geomagnetic conditions there is no discernible trend. This behavior suggests the possibility of different mechanisms influencing SAPS during geomagnetically quiet conditions. Average cross‐SAPS potentials increase with geomagnetic activity and typically vary between 15 and 45 kV. Finally, a new empirical model of SAPS potentials has been developed parameterized by Asy‐H index, MLT, and magnetic latitude.