COMPASS: a new COnductance Model based on PFISR And SWARM Satellite observations
• Zihan Wang,
• Shasha Zou
Zihan Wang
University of Michigan-Ann Arbor

Corresponding Author:wzihan@umich.edu

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Shasha Zou
University of Michigan-Ann Arbor
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## Abstract

Ionospheric conductance plays a crucial and active role in magnetosphere-ionosphere-thermosphere coupling processes. Despite its importance, direct global observations of conductance are unavailable. This limitation inspires the development of empirical models that are widely used to specify global distributions of conductance indirectly. In this work, a new model (COMPASS) describing the statistical relationships between conductance and Field-Aligned Currents (FACs) is presented. The conductance was determined by the electron densities measured by Poker Flat Incoherent Scattering Radar (PFISR), and the FACs were determined by the magnetic perturbations measured by SWARM. Between 2014 and 2020, there were $\sim$3900 conjunction events between PFISR and SWARM, providing a large dataset for investigating the relationship between conductance and FACs. It is found that both Hall and Pedersen conductances vary as a power of $|j_{\parallel}|$, and the power index $a$ is between 0 and 0.5. This power index $a$ depends on the Magnetic Local Time (MLT) and the direction of FACs: (1) The largest power index is obtained on the dawn side, and the minimum is at noon, suggesting the strongest/weakest correlation in the dawn/noon sector; (2) the power indices are positive for both upward and downward FACs and are larger for upward FACs than downward FACs, except in the dusk sector. The underlying physical mechanisms of the observed variations of the model parameters are also discussed. This work sheds light on the complicated relationship between FACs and conductance and provides a convenient way to specify global distributions of the auroral zone conductance.
Feb 2022Published in Space Weather volume 20 issue 2. 10.1029/2021SW002958