INFLUENCE OF INTERPLANETARY MAGNETIC FIELD By ON THEFIELD ALIGNED CURRENT IN THE MAGNETOPAUSE
行星际磁场By分量对地球磁层顶场向电流调制

Recent satellite observations and ground-based observations show that the interplanetary conditions have a strong influence on the field-aligned current (FAC) of the earth. This paper studies the influence of interplanetary magnetic field B y component on the FAC in the reconnection region of magnetopause by means of 3D MHD simulation. B y influences the reconnection process and the associated FAC of the simulation region by dayside boundary magnetic field B by at x=-L x. Results show a rapid increase of B by can increase FAC remarkably, sometimes about one order larger. Larger B by can also maintains FAC at a high level. In addition, asymmetric distribution of B y in the reconnection region caused by B by gives rise to the asymmetry of FAC. These results are in good agreement with satellite observations. Because FACs at the inner side of the reconnection layer flow into the polar ionosphere along magnetic field lines, the results are very important to better understanding of coupling of Solar wind-magnetosphere-ionosphere.