Variation of dependence of the cusp location at different altitude on the dipole tilt

Abstract

Using the Cluster cusp crossings data, dependence of the cusp location at the mid-altitude on the geomagnetic dipole tilt during northward IMF is studied. The results show that the cusp center moves 0.051° Invariant Latitude (ILAT) upon the increase of 1° in the dipole tilt angle at the average altitude of 5.8 RE (Earth radius). According to the present results obtained at the altitude of the Cluster orbit and previous results obtained at other altitudes of other satellite orbits, it is found that the higher the altitude in the cusp region is, the bigger the dependence of cusp location on the dipole tilt angle will be. If the altitude increases by 1 RE in the cusp region, the dependence will increase by 0.012° ILAT upon the increase of 1° in the dipole tilt angle. Some possible physical mechanisms are discussed and it shows that the cusp location will be more sensitive to the solar wind dynamic pressure if the altitude is high.