Abstract
This study exploits the volumetric sampling capabilities of the Resolute
Bay Incoherent Scatter Radar (RISR-N) in collaboration with all-sky
imagery and in-situ measurements (DMSP) to examine the interplay between
cold plasma transport and auroral precipitation during a high-latitude
lobe reconnection event on the dawn side. The IMF had an impulsive
negative excursion in B$_z$ embedded within a prolonged period of
B$_z>0$ and B$_y<0$. The combined effects
of transport and magnetic stress release associated with a reconnection
pulse resulted in a co-mingling of plasma patches and soft electron
precipitation, creating regions of elevated electron density and
temperature. Altitude profiles of ionospheric parameters extracted in
the rest frame of the drifting patch showed an increase in $T_e$
above 200 km and $N_e$ below 250 km (both hallmarks of soft
precipitation), while also showing small and predictable changes in
$N_e$ near the F-region peak over the 34-minute duration of the
event. For the first time, we identified that the simultaneous
appearance of elevated $T_e$ and elevated F-region $N_e$ (i.e., a
‘hot patch’), thus providing a new formation process for hot patches.
The physics-based GEMINI model was used to explore the response to the
observed precipitation as a function of altitude and time. Enhancements
in $N_e$ in the topside ionosphere (e.g., DMSP altitudes) are caused
by upward ambipolar diffusion induced by ionospheric heating and not
impact ionization. The study highlights the importance of densely
distributed measurements in space and time for understanding both
mesoscale and small-scale ionospheric dynamics in regions subject to
complex forcing.