Linking Very Near‐Earth Reconnection (VNERX) to Mid‐Latitude GICs: Evidence From the 7 September 2017 Storm | CU Experts

AbstractGeomagnetically Induced Currents (GICs) are a hazard to power systems. In this letter, we present a case study to understand why a Sudden‐Commencement‐associated 20A GIC spike, measured at mid‐latitude in Virginia, US, increased to 30A within 2 min of interplanetary shock arrival. We use high‐resolution ground magnetometer and in situ satellite data to infer that the shock at 23:00 UT on 7 September 2017 triggered Very‐Near‐Earth Reconnection (VNERX) near dusk. Empirical modeling, using data mining approach, corroborates the occurrence of reconnection within ∼10–12 RE. We argue the preceding interval of southward and westward Interplanetary Magnetic Field enhanced the duskside plasma sheet's susceptibility to VNERX by passage of a nearly frontal shock. To the best of our knowledge, we show for the first time an observational link between inferred‐VNERX and mid‐latitude GIC spike. This finding underscores the complexity a prediction model must capture to accurately predict peak GIC.

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