Analyzing The Global Evolution Of The Storm Ring Current From Ground Geomagnetic Observatories And Numerical Simulations

Based on the multipoint data analysis method, the evolution of the storm ring current has been investigated, and the new definitions for the storm symmetric and asymmetric indices have been obtained with the measurements of the ground geomagnetic observatories. On the other hand, a model of the distribution of the ring current particles has been established, and the ring current flux has been calculated.1. Based on the multipoint data analysis method, the spatial gradient of the corrected H component can be obtained from the continuous magnetic measurements of the multiple ground observatories. Assuming the geomagnetic disturbance around Earth’s surface is approximately linearly varying in space, new formulas of the physical definitions to the symmetric index and asymmetric index have been established, and the evolution of the storm ring current is deduced accordingly. It is found that the new defined symmetric index is generally consistent with the traditional one. The new defined asymmetric index is in substantial agreement with traditional one, and they have the same variation trend. The anti-direction of the gradient of the corrected H component can be regarded as pointing to the position of the maximum partial ring current. It is shown that, for ordinary magnetic storms with Dst>-200 nT, the maximum partial ring current is located around the duskside during the main phase and the earlier stage of the recovery phase. At the later stage of the recovery phase, the position of the maximum partial ring current can possibly keep rotating eastward. For the super storms(Dst<-200nT), the position of the maximum partial ring current is not as regular, and usually located at the dayside.2. The spatial gradient of the H component of the geomagnetic disturbance field has been obtained from ground geomagnetic observatories only in the eastern hemisphere, provided the geomagnetic disturbance field varies approximately linearly in space. Furthermore, the storm symmetric and asymmetric indices have been yielded, and the spatial distribution and temporal evolution of the storm ring current have been investigated. It is found that the storm indices derived from the locally distributed observatories in the Eastern Hemisphere are consistent with those officially published Kyoto standard indices which are from the globally distributed six observatories. We also have calculated the storm indices for 1952-1956 by using data from three stations(HER, KAK and SJG). There are good correlation between the storm indices derived from the three stations and those from the global six stations. Those results suggest that our approach is reasonable and significant when global ground observatories are not readily available in the early years.3. Based on the characteristic of the particles in the electromagnetic field and the conversation of the first and second adiabatic invariant, the kinetic formulas of the ring current particles have been established. And the ring current flux has been obtained. It is found that the ring current protons flux is increase with the L shell decrease. The stronger the geomagnetic disturbance is, the higher the proton energy and flux are. In the stable condition, the ring current protons assemble in the duskside. And in the unstable condition, the protons in the duskside keep westward drifting, and the partial ring current turn to the integrated ring current.