A Comparative Study of Ground Magnetic Variability Between High-Latitude Conjugate Chains to Characterize Interhemispheric Asymmetry During Geomagnetic Activity

Abstract

The Autonomous Adaptive Low-Power Instrument Platform magnetometer chain located in Antarctica has been operating since 2016 at a magnetically conjugate location to the West Greenland magnetometer chain, enabling interhemispheric evaluations of geomagnetic phenomena. Using 1-min resolution, three-dimensional magnetic field vector observations during geomagnetically active times throughout 2016–2022, we identified peak differences between conjugate magnetometer responses and statistically describe the time and amplitude differences that constitute an asymmetry. We found that a majority of asymmetric variations at these high-latitude locations consist of a response delay $\left(\Delta t\right)$ within 5 min. Further, approximately 20% of the qualifying difference peaks have no delay between responses, meaning there is a local maximum identified in both hemispheres within the same minute and the asymmetry is formed by a difference in response magnitude. To understand what physical processes might be responsible for the majority of asymmetric responses, we investigated the magnetic local time (MLT) distribution of ground magnetic variations associated with a response delay within 5 min. We found that for certain MLTs, asymmetries with a $\Delta t\le 5$ min are consistent with interhemispheric differences in overhead field-aligned currents (FACs). The MLT range that overhead FACs seem to be a primary driver is latitude dependent, shifting from noon at high latitudes toward earlier MLTs at lower latitudes. Understanding the variability of the interhemispheric responses with respect to overhead FACs has far-reaching implications for unraveling how magnetosphere-ionosphere systems couple.