Quantifying Hemispheric Asymmetry of Auroral Currents by Polar Region Interhemispheric Magnetic Observatories (PRIMO)

Previous observations have demonstrated that substorm auroras and the associated electric currents can exhibit substantial north-south asymmetry. Possible mechanisms that cause this asymmetry include the penetration of IMF By into the magnetotail, the difference in ionospheric conductivity due to the dipole tilt angle, and the difference in solar wind dynamo efficiency due to IMF Bx combined with the tilt angle. The relative importance of these factors, however, has not been determined, due to paucity of observations in the southern hemisphere. To resolve this difficulty, we propose to establish three new stations in West Antarctica for measuring geomagnetic perturbations. The three magnetometer stations are located at Lepley Lunatak, Union Glacier, and Whitmore Mountains, between -2° W and 7° W magnetic longitude at L-values 4, 6, and 8. These locations are magnetically conjugate to the recently established AUTUMNX magnetometers along the eastern shore of the Hudson Bay, enabling unique conjugate observations by two magnetometer chains at auroral latitudes and subauroral latitudes when close to midnight. These conjugate magnetic field observations, with concurrent satellite measurements by the AMPERE constellation and the Heliophysics System Observatory, can differentiate between magnetospheric and ionospheric contributions in the hemispheric asymmetry. The comparison with the conjugate observations at the Syowa and Iceland stations can shed light on the longitudinal extent of the hemispheric asymmetry. The PRIMO fluxgate magnetometer system includes a dedicated power and data communications platform developed by UNAVCO and successfully operated at ANET stations in the same region. The three PRIMO systems are co-located with existing ANET stations, facilitating logistic efficiencies such as transportation, cross-trained personnel, and common components. Our plan follows recommendations by the latest Heliophysics Decadal Study for ground-based observations, focusing on the American longitudinal sector and leveraging infrastructure through international collaborations.