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Abstract Solar eclipses present a rare glimpse into the impact of ionospheric electrodynamics on the magnetosphere independent of other well studied seasonal influences. Despite decades of study, we still do not have a complete description of the conditions for geomagnetic substorm onset. We present herein a mutual information based study of previously published substorm onsets and the past two decades of eclipses which indicates the likelihood of co‐occurrence is greater than random chance. A plausible interpretation for this relation suggests that the abrupt fluctuations in ionospheric conductivity during an eclipse may influence the magnetospheric preconditions of substorm initiation. While the mechanism remains unclear, this study presents strong evidence of a link between substorm onset and solar eclipses. 

Abstract Dipolarizing flux bundles (DFBs) have been suggested to transport energy and momentum from regions of reconnection in the magnetotail to the high latitude ionosphere, where they can generate localized ionospheric currents that can produce large nighttime geomagnetic disturbances (GMDs). In this study we identified DFBs observed in the midnight sector from ∼7 to ∼10 R_Eby THEMIS A, D, and E during days in 2015–2017 whose northern hemisphere magnetic footpoints mapped to regions near Hudson Bay, Canada, and have compared them to isolated GMDs observed by ground magnetometers. We found 6 days during which one or more of these DFBs coincided to within ±3 min with ≥6 nT/s GMDs observed by latitudinally closely spaced ground‐based magnetometers located near those footpoints. Spherical elementary current systems (SECS) maps and all‐sky imager data provided further characterization of two events, showing short‐lived localized intense upward currents, auroral intensifications and/or streamers, and vortical perturbations of a westward electrojet. On all but one of these days the coincident DFB—GMD pairs occurred during intervals of high‐speed solar wind streams but low values of SYM/H. The observations reported here indicate that isolated DFBs generated under these conditions influence only limited spatial regions nearer Earth. In some events, in which the DFBs were observed closer to Earth and with lower Earthward velocities, the GMDs occurred slightly earlier than the DFBs, suggesting that braking had begun before the time of the DFB observation. 

This dataset contains 1-second vector magnetic field measurements (Bx, By, Bz; nT) from the ZK3 fluxgate magnetometer station (75°54′14″S, 76°50′24″E, SYS8) on the East Antarctic Plateau. Data were collected from 31 January 2023 to 22 February 2023 as part of the AAL-PIP array and are stored in hourly files named by UT creation time. Seasonal data gaps may occur during the Antarctic winter due to power limitations. 

This dataset contains 1-second vector magnetic field measurements (Bx, By, Bz; nT) from the ZK1 fluxgate magnetometer station (75°31′12″S, 77°38′24″E) on the East Antarctic Plateau. Data were collected from 14 December 2022 to 8 May 2023 as part of the AAL-PIP array and are stored in hourly files named by UT creation time. Seasonal data gaps may occur during the Antarctic winter due to power limitations. 

The AAL-PIP collection of magnetometers is part of an autonomous adaptive low-power instrument platform (AAL-PIP) chain of six stations that has been established on East Antarctic Plateau along the 40 deg geomagnetic meridian, to investigate interhemispheric geomagnetically conjugate current systems, waves, and other space weather phenomena in Polar Regions. These six stations, PG0 to PG5, which run autonomously with solar power and two-way satellite communication, are designated at the geomagnetically conjugate locations of the West Greenland geomagnetic chain covering magnetic latitudes from 70 deg to 80 deg. 

Geomagnetic Ultra Low Frequency (ULF) are terrestrial manifestations of the propagation of very low frequency magnetic fluid waves in the magnetosphere, and it is critical to develop near real-time space weather products to monitor these geomagnetic disturbances. A wavelet-based index is described in this paper and applied to study geomagnetic ULF pulsations observed in Antarctica and their magnetically conjugate locations in West Greenland. Results showed that (1) the index is effective for identification of pulsation events in the Pc4–Pc5 frequency range, including transient events, and measures important characteristics of ULF pulsations in both the temporal and frequency domains. (2) Comparison between conjugate locations reveals the similarities and differences between ULF pulsations in northern and southern hemispheres during solstice conditions, when the largest asymmetries are expected. Results also showed that the geomagnetic pulsations at conjugate locations respond differently according to the Interplanetary Magnetic Field condition, magnetic field topology, magnetic latitude of the observation, and other conditions. The actual magnetospheric and ionospheric configurations and driving conditions in the case need to be further studied. 

Key Points Magnetic field measurements are obtained from magnetic conjugate points in both hemispheres Under optimal conditions the conjugate magnetic fields are very similar, with signs reversed on two components due to coordinate geometries More often the fields differ due to different seasonal conductivities and asymmetrical driving by the magnetic field in the solar wind 

Key Points Magnetospheric Multiscale observed a series of foreshock transients near the Earth's bow shock Pc1 waves and magnetic impulse events are observed by ground magnetometers in both hemispheres following the foreshock transients The difference in observation times between hemispheres implies that Pc1 waves are generated in the off‐equatorial region 

Models for space weather forecasting will never be complete/valid without accounting for inter-hemispheric asymmetries in Earth’s magnetosphere, ionosphere and thermosphere. This whitepaper is a strategic vision for understanding these asymmetries from a global perspective of geospace research and space weather monitoring, including current states, future challenges, and potential solutions.