Seasonal and solar cycle dependence of energy transfer rates in the
Auroral E-region
Abstract
We report one of the first comprehensive ground-based investigations of
energy transfer rates in the E-region ionosphere compared relative to
geomagnetic activity, seasonal effects, and solar activity level using
nearly continuously sampled data collected with the Poker Flat
Incoherent Scatter Radar (PFISR) between 2010-2019. We quantified the
integrated electromagnetic (EM) energy transfer rate and the integrated
Joule heating rate in the E-region between 90-130 km, which includes the
contributions from the neutral winds. We find that (1) the median Joule
heating rate and electromagnetic (EM) energy transfer rate in the
evening sector is larger in the winter versus the summer and have
similar magnitudes in the spring and fall for the same solar activity
and geomagnetic conditions. (2) The seasonal dependence of the energy
transfer rates is closely associated with the seasonal variations of the
electric fields. Our analysis shows that the larger EM energy transfer
and Joule heating rates in disturbed conditions in the winter versus the
summer are associated with the combined effects of both the electric
field and Pedersen conductance with the electric field playing a
dominant role. Given that the Pedersen conductance in the evening sector
is closely related to the particle precipitation and field-aligned
currents in the auroral region, this study provides complementary
ionospheric evidence of the winter-summer asymmetry of the intensity and
density of field-aligned currents (e.g. Ohtani et al., 2009). (3) The
geomagnetic activity level has the most significant impacts on the
magnitude of the energy transfer rates, followed by seasonal variations,
and last the solar activity level.