Geophysical Research Letters

Ionospheric outflow and cross polar cap potential: What is the role of magnetospheric inflation?

Authors

  • D. T. Welling,

    Corresponding author
    1. Los Alamos National Laboratory, Los Alamos, New Mexico, USA
    2. Now at Department of Atmospheric, Oceanic and Space Sciences, Ann Arbor, Michigan, USA
      Corresponding author: D. T. Welling, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143, USA. (dwelling@umich.edu)
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  • S. G. Zaharia

    1. Los Alamos National Laboratory, Los Alamos, New Mexico, USA
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Corresponding author: D. T. Welling, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143, USA. (dwelling@umich.edu)

Abstract

[1] Reductions of the ionospheric cross polar cap potential in magnetohydrodynamic models that include polar wind-like heavy ion outflow have become a ubiquitous observation in recent studies. The underlying mechanisms for these reductions, which are not to be confused with the problem of potential saturation, remain in question. A possible explanation is that such outflow inflates the magnetosphere, creating a blunter obstacle to the solar wind and reducing the upstream geoeffective length. Such an explanation is attractive because it describes the outflow-related potential drop in clear, model-independent terms. This study uses three separate magnetohydrodynamic simulations to test this hypothesis: one coupled to a polar wind outflow model, one coupled to an inner magnetosphere code in order to reproduce the effect without explicit outflow, and a stand-alone baseline simulation. It is found that this hypothesis cannot explain the total reduction. Results suggest that other mechanisms, such as a change to the dayside reconnection rate, may be important, but further investigation is required.

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