Solar Extreme Events of 2003:
Fundamental Science and Applied Aspects

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Predictions of the magnetospheric electric currents during superstorms
Maltsev Y.P., Ostapenko A.A., Pchelkin V.V.,

The predictions are mostly based on extrapolation of the results obtained for less disturbed periods, complemented by a few measurements taken during superstorms. The electric currents for quiet and moderate storm conditions were found statistically from the databases of \textit{Fairfield et al}. [1994] (about 70,000 magnetic measurements mainly for \textit{Dst} > $ - $70 nT) and \textit{Tsyganenko et al}. [2003] (140,000 magnetic data for \textit{Dst} > $ - $200 nT). The magnetic fields from these databases were averaged in spatial bins with 2 $R_{E}$ resolution for five \textit{Dst} ranges. Then the electric current density was calculated. The total dayside electric current can be expressed by the following empirical formula: $I_{{\rm n}{\rm o}{\rm o}{\rm n}}$ = 0.8 -- \textit{Dst}/115, where $I$ is in MA. Extrapolation to a superstorm with \textit{Dst} = $ - $450 nT yields the dayside current $\sim $5 MA. We obtained the following approximation formula for the nightside current at distances from 4 to 9 $R_{E}$: $I_{{\rm n}{\rm i}{\rm g}{\rm h}{\rm t}}$ = 2 -- \textit{Dst}/15, which predicts $\sim $30 MA current for \textit{Dst} = $ - $450 nT. We did not reveal any pronounced dawn-dusk asymmetry in the currents for both databases. One can conclude that the main contribution to \textit{Dst} during superstorms is due to the nightside electric currents.

Skobeltsyn Institute of Nuclear Physics, Moscow State University, 2004