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.