Storm time coupling between the magnetosheath and the polar ionosphere

Abstract

The present study demonstrates the feasibility of using plasma and magnetic field data from Defense Meteorological Satellite Program (DMSP) satellites to estimate the Alfvénic reflectances (α) in the polar cap ionosphere during periods of geomagnetic disturbance. Quantitative values of α are then used to support calculations of field-aligned Poynting flux (S||i) transmitted along open field lines from magnetosheath generators to the conjugate polar ionospheres. Analyzed data were acquired during high-latitude passes of DMSP F16 during the 17 March 2013 magnetic storm. Between the main phase onset and the day's end, plasma velocity and magnetic field perturbations manifest the phase relations predicted by Alfvén and Fälthammar (1963) for electromagnetic coupling. The most reliable (sunward-antisunward) components of measured plasma velocities and magnetic perturbations are consistent with that α ranging between 0.65 and 0.97, with a mean of ~0.8. Subsequent calculations indicate that incident S||i varied between 0.2 and 0.02 W/m2 with a mean of 0.085. We suggest that these reported ranges of α and S||i reflect both large variations in IMF BZ and the growth of antisunward neutral winds in the polar caps during the storm's main phase.