SIMULATION OF STORM-TIME PARTIAL RING CURRENT SYSTEM AND THE DAWN DUSK ASYMMETRY OF GEOMAGNETIC-VARIATION

We simulated the ring current using a monochromatic model and obtained the temporal variation of the divergence of the ring current. Next, assuming that the divergence of the ring current closes by the field-aligned currents, we simulated the ionospheric currents and estimated the geomagnetic variation on the earth surface. We found that our results of the variation of the H component at mid-latitudes caused by the field-aligned current agree with observational results. The simulated asymmetry of the H component is much larger than the simulated symmetric part of the H component. This suggests that some part of the D(st) development is caused by a ring current which does not have the current divergence.