Simulating the three-dimensional ionospheric current system

Abstract:

Ionospheric electric fields and currents are driven by collisional
interaction between thermospheric winds and ions, by
magnetospherically driven ion 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.
For time scales longer than a few minutes the electric field
is electrostatic. It is also a reasonable assumption that the electric potential is
nearly constant along geomagnetic-field lines. Therefore the
electric field can be represented in two dimensions in a
coordinate system aligned with the geomagnetic field. 
The current density, however, which depends also on the conductivity
distribution, varies in all three dimensions. 
We are developing a model of ionospheric electrodynamics that
takes into account the wind dynamo, the magnetospheric
field-aligned current, and gravitational and pressure
gradient forces to calculate the three-dimensional structure of currents and
their associated magnetic perturbation fields at the Earth's surface
and at Low Earth Orbit (LEO) satellite altitudes.

We will use this model to examine the effects of the different
sources on the 3-dimensional currents and their associated
magnetic perturbations. An accurate description of the 3D ionospheric
currents is critically important to interpreting satellite observations
at LEO height as they are affected by the various atmospheric
forces all together. In this presentation we will
introduce the new capabilities of calculating the
3-dimensional ionospheric current and magnetic perturbations.
With selected examples we will illustrate the currents and magnetic
perturbations produced by the neutral wind
during quiescent and geomagnetic active times,
and those produced by gravity and plasma pressure-gradient forces on the plasma.
We will discuss possible improvements in the modelling
of ionospheric currents driven by magnetospheric sources.