Storm-time Dynamics of Birkeland Currents: Testing and Improving Physics-based Predictions

Tuesday, 12 February 2019: 11:30
Fountain I/II (Westin Pasadena)
Brian J Anderson, Johns Hopkins Univ, Laurel, MD, United States, Sarah K. Vines, Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, Robin J Barnes, JHU/APL, Laurel, MD, United States, Michael Warren Liemohn, University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States and Michael G Henderson, Los Alamos National Laboratory, Los Alamos, NM, United States
Abstract:
A number of space weather effects are linked to electrodynamics typically occurring at high-latitudes associated with the auroral zones. These include dynamics of drag for satellites and debris in LEO related to thermospheric heating, scintillation associated with ionospheric density irregularities and structures affecting navigation and communications, auroral precipitation related to spacecraft charging, and geomagnetically induced currents affecting the utility power network. During more extreme space weather events, these phenomena extend to middle latitudes. Empirical statistical analyses of typical conditions may be of limited use because the events of greatest interest are relatively infrequent and these techniques tend to smear out dynamically important aspects of active-time conditions. Alternatively, physics-based simulations can be used to estimate dynamics of strong storms. It is not clear that simulation codes validated for nominal conditions apply to the storm-time system because the coupling between the ionosphere/thermosphere and magnetosphere may change dramatically. Potential non-linear responses include heavy ion outflows, intense thermospheric heating and upwelling, intense ionospheric precipitation and transport, unprecedented thermospheric winds, and intense magnetospheric plasma pressures. Simulations including feedback dynamics must be tested against observations to quantify their reliability. We have identified the most intense storms between 1 January 2010 and January 2017. During this time, there were over two-dozen geomagnetic storms, five of which had minimum SymH of -150 nT or lower. Using this set of storms, we examine the dynamics of the Birkeland currents measured continuously and globally by AMPERE. Comparisons of the AMPERE results with physics-based simulations for the two strongest storms in the period, 17-18 March 2015 and 22-23 June 2015, are presented to assess the extent to which the simulations capture the dynamics of the Birkeland currents during these storms.
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