High-latitude electrodynamics specified in SAMI3 using AMPERE
field-aligned currents
Abstract
A new technique has been developed in which the high-latitude electric
potential is determined from field-aligned current observations from the
Active Magnetosphere and Planetary Electrodynamics Response Experiment
(AMPERE) and conductances modeled by Sami3 is Also a Model of the
Ionosphere (SAMI3). This is a development of the
Magnetosphere-Ionosphere Coupling (MIX) approach first demonstrated by
Merkin and Lyon (2010). An advantage of using SAMI3 is that the model
can be used to predict Total Electron Content (TEC) in the polar caps,
based on the AMPERE-derived potential solutions. 23 May 2014 is chosen
as a case study to assess the new technique for a moderately disturbed
case (min Dst: -36 nT, max AE: 909 nT) with good GPS data coverage. The
new AMPERE/SAMI3 solutions are compared against independent GPS-based
TEC observations from the Multi-Instrument Data Analysis Software
(MIDAS) by Mitchell and Spencer, 2003, and against Defense
Meteorological Satellite Program (DMSP) ion drift data. The comparison
shows excellent agreement between the location of the tongue of
ionization in the MIDAS GPS data and the AMPERE/SAMI3 potential pattern,
and good overall agreement with DMSP drifts. SAMI3 predictions of
high-latitude TEC are much improved when using the AMPERE-derived
potential as compared to that of the Weimer (2005) model. The two
potential models have substantial differences, with Weimer producing an
average 77 kV cross-cap potential versus 60 kV for the AMPERE-derived
potential. The results indicate that the 66-satellite Iridium
constellation provides sufficient resolution of field-aligned currents
to estimate large-scale ionospheric convection as it impacts TEC.