Cluster signatures of ionospheric density cavities: a smoking gun for ionospheric feedback in black auroras
Open Session on Magnetospheric, Ionospheric and Solar-Terrestrial physics
Alexander Russell
Tomas Karlsson (KTH Royal Institute of Technology), Andrew Wright (University of St Andrews)
University of Dundee
We present Cluster measurements of large amplitude electric fields correlated with intense downward field-aligned currents, observed during a nightside crossing of the auroral zone. The data are reproduced by a simple model of magnetosphere-ionosphere coupling, which, under different conditions, can also produce a divergent electric field in the downward current region or a correlation between electric and perturbed magnetic fields. We conclude that a strong electric field associated with intense downward field-aligned current, such as this observation, is a signature of ionospheric plasma depletion caused by the downward current. The results are some of the strongest evidence to date that the ionosphere actively influences the structure and dynamics of black auroras.
16:30 - 18:00