Field‐Aligned and Ionospheric Currents by AMPERE and SuperMAG During HSS/SIR‐Driven Storms
Field‐Aligned and Ionospheric Currents by AMPERE and SuperMAG During HSS/SIR‐Driven Storms
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DOI：
10.1029/2021ja029437
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发表时间：
2021-04
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影响因子：
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通讯作者：
M. Pedersen;H. Vanhamäki;A. Aikio;S. Käki;A. Workayehu;C. Waters;J. Gjerloev
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作者：
M. Pedersen;H. Vanhamäki;A. Aikio;S. Käki;A. Workayehu;C. Waters;J. Gjerloev
本研究考虑了 2010 年至 2017 年期间由高速流 (HSS) 和相关流相互作用区域 (SIR) 驱动的 28 个 Dst ≤−50 nT 的地磁风暴。分别使用 SuperMAG 和 AMPERE 数据的叠加历元分析研究了它们对电离层水平电流和场对准电流 (FAC) 的影响。零纪元 (t0) 被设置为风暴主阶段的开始。风暴从 SIR 开始，太阳风密度增强，磁场向南压缩。积分 FAC 和等效电流分别在 t0 之后 40 分钟和 58 分钟达到最大值，随后在主阶段中间（t0 + 4 小时）出现一个小峰值，并在 Dst 最小值（t0 + 5.3 小时）之前出现一个稍大的峰值。这些电流受到太阳风的强烈驱动，Akasofu ε 与积分 FAC 之间的相关性为 0.90。亚暴爆发的数量在 t0 附近达到最大值。根据 SIR 附近的太阳风动压 pdyn，风暴也被分为两组。与低 pdyn 事件相比，高 pdyn 风暴更早达到太阳风速最大值，并且从 HSS 到达到风暴爆发的前置时间更短。高 pdyn 事件还具有突然的风暴开始、更强的太阳风驱动和 t0 时的电离层响应，并且是造成 t0 后电流的第一个峰值的主要原因。 t0+2天后，与高pdyn事件相比，低pdyn事件的海流和亚暴爆发次数变得更高，这可能与较高的太阳风速有关。
This study considers 28 geomagnetic storms with Dst ≤−50 nT driven by high‐speed streams (HSSs) and associated stream interaction regions (SIRs) during 2010–2017. Their impact on ionospheric horizontal and field‐aligned currents (FACs) have been investigated using superposed epoch analysis of SuperMAG and AMPERE data, respectively. The zero epoch ( t0 ) was set to the onset of the storm main phase. Storms begin in the SIR with enhanced solar wind density and compressed southward oriented magnetic field. The integrated FAC and equivalent currents maximize 40 and 58 min after t0 , respectively, followed by a small peak in the middle of the main phase ( t0 + 4 hr), and a slightly larger peak just before the Dst minimum ( t0 + 5.3 hr). The currents are strongly driven by the solar wind, and the correlation between the Akasofu ε and integrated FAC is 0.90. The number of substorm onsets maximizes near t0 . The storms were also separated into two groups based on the solar wind dynamic pressure pdyn in the vicinity of the SIR. High pdyn storms reach solar wind velocity maxima earlier and have shorter lead times from the HSS arrival to storm onset compared with low pdyn events. The high pdyn events also have sudden storm commencements, stronger solar wind driving and ionospheric response at t0 , and are primarily responsible for the first peak in the currents after t0 . After t0+2 days, the currents and number of substorm onsets become higher for low compared with high pdyn events, which may be related to higher solar wind speed.