Abstract
We have used empirical models for electric potentials and the magnetic
fields in both space and on the ground to obtain maps of the
height-integrated Pedersen and Hall ionospheric conductivities at high
latitudes. This calculation required use of both “curl-free” and
“divergence-free” components of the ionospheric currents, with the
former obtained from magnetic fields that are used in a model of the
field-aligned currents. The second component is from the equivalent
current, usually associated with Hall currents, derived from the
ground-level magnetic field. Conductances were calculated for varying
combinations of the Interplanetary magnetic field (IMF) magnitude and
orientation angle, as well as the dipole tilt angle. The results show
that reversing the sign of the Y component of the IMF produces
substantially different conductivity patterns. The Hall conductivities
are largest on the dawn side in the upward, Region 2 field-aligned
currents. Low electric field strengths in the Harang discontinuity lead
to inconclusive results near midnight. Calculations of the Joule
heating, obtained from the electric field and both components of the
ionospheric current, are compared with the Poynting flux in space. The
maps show some differences, while their integrated totals match to
within 1%. Some of the Poynting flux that enters the polar cap is
dissipated as Joule heating within the auroral ovals, where the
conductivity is enhanced, confirming the Poynting Flux theorem proposed
by Richmond in 2010, for the first time using realistic electric fields,
ionospheric currents, and conductivity.