Estimating Ionosphere Conductance on Global Spatial Scales

Abstract:

The ionosphere represents the Earthward boundary of space. For large scale processes, the height integrated conductivities (conductances) of the ionosphere are known to modulate the energy transfer between the magnetosphere and ionosphere. Estimating the Pedersen and Hall conductances on a global scale, particularly in the auroral regions, is fundamental to understanding the dynamics of the high latitude ionosphere and thermosphere. Experimental measurements with sufficient spatial coverage and with time scales of order of minutes or less are required. While the spatial coverage of HF radar and spacecraft measurements has recently improved, it turns out that the most challenging aspects for global estimates of ionosphere conductance are directly related to ground-based magnetometer data.

The Iridium satellite constellation consists of more than 70 satellites in circular, polar, 780 km altitude orbits which provides a unique opportunity to obtain in-situ measurements of the global distribution of the Birkeland currents and associated magnetic field perturbations. In this paper, examples and challenges for combining the Iridium satellite, HF radar and ground magnetometer data in order to produce estimates of the Pedersen and Hall conductances on global spatial scales will be presented. We discuss limiting factors in the methodology and some possible alternatives.