A first generation numerical geomagnetic storm prediction scheme

Abstract

Geomagnetic and auroral disturbances cause significant interference on many electrical systems. Therefore, it is essential to develop a reliable geomagnetic and auroral storm prediction scheme. Present geomagnetic storm prediction schemes rely entirely on statistical results, so that they can hardly provide quantitative information on the intensity of a geomagnetic storm caused by a particular solar event. It is for this reason that we have been developing a first generation numerical prediction scheme. The scheme consists of two major computer codes which in turn consist of a large number of subroutine codes and of empirical relationships. First of all, when a solar flare occurs, six flare parameters are determined as the input data set for the first code which is devised to show the simulated propagation of solar wind disturbances in the heliosphere to a distance of 2 a.u. Thus, one can determine the relative location of the propagating disturbances with the Earth's position. The solar wind speed ( V) and the three interplanetary magnetic field (IMF) components ( B x , B y , B z , or B, 0, φ) are then computed as a function of time at the Earth location or any other desired (space probe) locations. These quantities in turn become the input parameters for the second major code which computes first the power (ϵ) of the solar wind-magnetosphere dynamo as a function of time. The power thus obtained and the three IMF components can be used to compute or infer: (i), the predicted geometry of the auroral oval; (ii), the cross-polar cap potential; (iii), the two geomagnetic indices AE and Dst; (iv), the total energy injection rate into the polar ionosphere; (v), the atmospheric temperature, etc. At the present time, the weakest part of the scheme arises from the fact that causes of changes of the IMF B z (or θ) component are not well understood. Further, several empirical relationships are incorporated in the present scheme in the second major code. Thus, there are still a number of solar and geomagnetic storm features which require theoretical studies and proper modeling efforts to eventually replace the empirical relationships by theoretical ones, as our understanding of solar-terrestrial physics advances.