This work conducts a statistical study of the subauroral polarization stream (SAPS) feature in the North American sector using Millstone Hill incoherent scatter radar measurements from 1979 to 2019, which provides a comprehensive SAPS climatology using a significantly larger database of radar observations than was used in seminal earlier works. Key features of SAPS and associated electron density (Ne), ion temperature (Ti), and electron temperature (Te) are investigated using a superposed epoch analysis method. The characteristics of these parameters are investigated with respect to magnetic local time, season, geomagnetic activity, solar activity, and interplanetary magnetic field (IMF) orientation, respectively. The main results are as follows: (1) Conditions for SAPS are more favorable for dusk than near midnight, for winter compared to summer, for active geomagnetic periods compared to quiet time, for solar minimum compared to solar maximum, and for IMF conditions with negative By and negative Bz. (2) SAPS is usually associated with a midlatitude trough of 15–20% depletion in the background density. The SAPS‐related trough is more pronounced in the postmidnight sector and near the equinoxes. (3) Subauroral ion and electron temperatures exhibit a 3–8% (50–120 K) enhancement in SAPS regions, which tend to have higher percentage enhancement during geomagnetically active periods and at midnight. Ion temperature enhancements are more favored during low solar activity periods, while the electron temperature enhancement remains almost constant as a function of the solar cycle. (4) The electron thermal content, Te × Ne, in the SAPS associated region is strongly dependent on 1/Ne, with Te exhibiting a negative correlation with respect to Ne.

中文翻译：

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使用Millstone Hill非相干散射雷达1979-2019年测量结果对北美地区的耳下极化流进行的统计研究

这项工作使用1979年至2019年的Millstone Hill非相干散射雷达测量数据对北美地区的极耳极化流（SAPS）特征进行了统计研究，该数据使用比以前使用的雷达观测数据库大得多的数据库提供了全面的SAPS气候学开创性的早期作品。SAPS的主要特征以及相关的电子密度（N e），离子温度（T i）和电子温度（T e）是使用重叠历元分析方法进行调查的。这些参数的特性分别针对磁性当地时间，季节，地磁活动，太阳活动和行星际磁场（IMF）方向进行了研究。主要结果如下：（1）SAPS的条件比黄昏更有利于午夜，冬天比夏天更适合冬季，相对于安静时间而言更适合于活跃的地磁时段，对于太阳最弱相对于最大太阳，以及IMF条件更有利。负B y和负B z。（2）SAPS通常与背景密度减少15-20％的中纬度谷有关。与SAPS相关的波谷在午夜之后和春分点附近更为明显。（3）在SAPS区域中，耳下离子和电子的温度升高了3–8％（50–120 K），在地磁活跃期和午夜期间，升高的百分比往往更高。在太阳活动低的时期，离子温度的提高更为有利，而电子温度的升高几乎保持恒定，这是太阳周期的函数。（4）SAPS关联区域中的电子热含量T e  ×  N e强烈取决于1 / N e，其中T e与N e呈负相关。