Modeling the three-dimensional structure of ionospheric electrodynamics

Abstract:

Ionospheric electric fields and currents are driven by collisional
interaction between thermospheric winds and ions, by
magnetospherically driven convection and field-aligned currents at
high latitudes, by gravitational and pressure-gradient forces on the
ionospheric plasma, and by weak currents from the lower atmosphere.
The electrodynamics of the ionospheric E and F regions are strongly
coupled. For time scales longer than a few minutes the electric field
is electrostatic. The electric potential is nearly constant along
geomagnetic-field lines, and can be represented in two dimensions in a
coordinate system aligned with the magnetic field. The current
density, however, varies in all three dimensions. The associated
perturbations of the geomagnetic field induce currents in the Earth,
which modify the perturbations.

We are developing a model of ionospheric electrodynamics that takes into account all of the sources
and calculates the three-dimensional structure of currents and
their associated magnetic perturbation fields at high spatial
resolution. This model will be used to simulate ionospheric drifts as
well as geomagnetic perturbations at the ground, at low-Earth-orbit
satellite heights, and within the E-region ionosphere. When coupled
with a dynamical model of the thermosphere and ionosphere it can be
used to assimilate electrodynamic data into the model. In this
presentation we discuss the modeling principles and present results
relevant to the electrodynamics of the middle and low latitude
ionosphere below 200 km, including the effects of coupling with
F-region electrodynamics and the expected observable effects on
rockets and on low Earth orbit satellites.