Auroral electrojets during geomagnetic storms

Abstract

On the basis of digital magnetometers from the International monitor auroral geomagnetic effects (IMAGE) and European incoherent scatter (EISCAT) meridional chains in Scandinavia dynamics of the eastward and westward electrojets during the main phase of magnetic storms are considered. For the intense magnetic storm on May 10–11, 1992, with Dst = −300 nT, magnetograms of subauroral and midlatitudinal stations Leningrad, Borok, and Moscow were examined. It is found that the eastward electrojet center during the storm main phase shifts equatorward as |Dst| increases. The electrojet center is located at the corrected geomagnetic latitude Φ ∼ 59°–60° when Dst ∼ −100 nT and at Φ ∼ 54°–55° when Dst ∼ −300 nT. Data from meridional chains of magnetometers support earlier results pertaining to the relationship between the westward electrojet center position and the ring current intensity for intervals between substorms. During substorms expansive phases the westward electrojet expands poleward covering auroral latitudes Φ ∼ 65°. The electrojets location during the storm main phase and their dynamics in connection with substorms allow for interpretations of effects described in the literature: the AE indices saturation during the main phase of magnetic storms; approximately equal values of AU and AL indices during the storm initial phase and AL ≫ AU during the storm main phase.