Empirical Study of Subauroral Polarization Streams (SAPS) through Decades of Satellite Observations
Landry, Russell Gerard
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Subauroral Polarization Streams (SAPS) are a phenomenon characterized by westward ion drifts driven by poleward electric fields in the subauroral ionosphere associated with field-aligned currents (FACs) generated by magnetospheric processes. In this dissertation, we have studied SAPS by analyzing the statistics of in-situ measurements of the subauroral ionosphere made by the Defense Meteorological Satellite Program (DMSP) and Dynamics Explorer 2 (DE 2) satellites. We have used these measurements to develop an empirical model of subauroral electric fields which is oriented relative to particle precipitation boundaries instead of by geomagnetic coordinates. This was done through the use of an auroral boundary model that we have developed to extrapolate the equatorward boundary identified at one local time to all others, which outperforms previous models for that purpose. We have investigated the correlations of the SAPS model with magnetometer derived indices which track magnetic activity, as well as variations with season, hemisphere, interplanetary magnetic field parameters, and solar flux. A geomagnetic storm SAPS model is also presented, as well as the statistical variation of SAPS during substorms. Along with the qualitative results the statistics have revealed, the models allow for a more realistic SAPS electric field to be incorporated into a global convection model to study the effects of SAPS on the thermosphere and plasmasphere.