Mean Energy Flux, Associated Derived Height-Integrated Conductances, and Field-Aligned Current Magnitudes Evolve Differently During a Substorm
Mean Energy Flux, Associated Derived Height-Integrated Conductances, and Field-Aligned Current Magnitudes Evolve Differently During a Substorm
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平均能量通量、相关导出的高度积分电导和场对准电流强度在亚暴期间变化不同
DOI：
10.1029/2022ja030942
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发表时间：
2023
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影响因子：
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通讯作者：
Carter J
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文献类型：
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作者：
Carter J
我们研究了亚暴过程中极冠夜侧区域降水引起的高度积分电导的平均演化，沿着场向电流（FACs）。电导是根据极光发射数据得出的平均能通量和平均能量来估计的。根据每个亚暴的开始和恢复阶段之间的时间（δt），在标准化时间网格上使用叠加历元分析对数据进行分箱。我们还使用宽度为0.25 hr的固定时间分箱检查电导。我们将数据集按起始磁纬度划分。我们发现，观测到的最高电导发生在磁纬63 °和65°之间的亚暴，峰值约为11 mho（Hall）和4.8 mho（Pedersen）。在高磁纬地区发生的亚暴，电导较低，变率较小。亚暴过程中的电导变化主要是由平均能量通量的变化（约40%）驱动的，而不是降水的平均能量。平均能量在爆发后比能量通量增加得慢，之后这些能量在最低纬度爆发时缓慢下降。未观察到主要区域1和区域2 FACs的明显扩张。然而，我们确实看到了电流大小与磁纬度的排序，特别是在上午扇区的FAC向下的区域1。峰值电流幅值发生在归一化和固定时间网格的恢复阶段开始之后或之前。
We examine the average evolution of precipitation‐induced height‐integrated conductances, along with field‐aligned currents (FACs), in the nightside sector of the polar cap over the course of a substorm. Conductances are estimated from the average energy flux and mean energies derived from auroral emission data. Data are binned using a superposed epoch analysis on a normalized time grid based on the time between onset and recovery phase (δt) of each contributing substorm. We also examine conductances using a fixed time binning of width 0.25 hr. We split the data set by magnetic latitude of onset. We find that the highest conductances are observed for substorms with onsets that occur between 63 and 65° magnetic latitude, peaking at around 11 mho (Hall) and 4.8 mho (Pedersen). Substorms with onsets at higher magnetic latitudes show lower conductances and less variability. Changes in conductance over the course of a substorm appear primarily driven by changes (about 40% at onset) in the average energy flux, rather than the average energy of the precipitation. Average energies increase after onset slower than energy flux, later these energies decrease slowly for the lowest latitude onsets. No clear expansion of the main region 1 and region 2 FACs is observed. However, we do see an ordering of the current magnitudes with magnetic latitude of onset, particularly for region 1 downwards FAC in the morning sector. Peak current magnitudes occur slightly after or before the start of the recovery phase for the normalized and fixed‐time grids.