Auroral vortex, poleward surge, and vortical current in the ionosphere associated with Pi2 pulsations: A case for westward propagation of the poleward surge

Abstract:

An auroral breakup event accompanying a westward propagating auroral surge at the poleward boundary of the auroral zone was observed during the interval 0500 - 0510 UT 27 January 1986 by all-sky imagers installed at GWR (65.7N, 358.6) and SHM (66.3N, 336.0), and by magnetometers at four ground stations in the auroral and sub-auroral zone. Results obtained are as follows:

1. Poleward expansion of the aurora accompanied the magnetic pulse on the order of ~400nT.

2. The ionospheric current loop propagating westward explained the wave polarizations of the magnetic pulse.

3. The vortex was also observed in auroras. The rotations were opposite to those of the current loop.

4. The auroral surge propagating poleward separated from the auroral vortex in lower latitudes.

The occurrence of a ground Pi2 signal in the auroral zone during the auroral breakup was consistent with the propagating loop current hypothesis [Pashin et al., 1982].

The loop current appeared in association with the violent motion of auroras breaking out of the onset latitudes.

References;Pashin et al., 1982, J.Geophys., 51, 223-233.