Simulation Smdy Of The Characteristics Of The Thermospheric Density Disturbance During The Magnetic Stom

In this paper, the distribution and variation of thermospheric density during geomagnetic storms are calculated by NCAR-TIEGCM model, and are compared and analyzed with the results of CHAMP/STAR, to evaluate the accuracy of the model, and the characteristics of the thermospheric density variation during geomagneitic storm are also studied.The thermospheric densities at the altitude of410km during the geomagnetic storm on Nov.20-21,2003are calculated by NCAR-TIEGCM model, and the results are compared and analysed with the observational data from CHAMP/STAR. The results show that the model can exactly represent the distribution and variation of the density during geomagnetic storm, and the model results have a good consistency with the CHAMP data in trends and orders. But some certain differences do exist in detail structure and magnitude. The deviations between the model and CHAMP at high latitude are bigger than those of low latitude, and dayside bigger than nightside. It is also found that the density disturbance during geomagnetic storm presents day-night asymmetry and Southern-Northern hemisphere asymmetry. The model can exactly represent the propagation of the density disturbance from high latitude to low latitude, and the time delay in response of the density to geomagnetic storm.The thermospheric densities during39large geomagnetic storm events from2001to2005are statistical studied. Using CHAMP/STAR density data, the relationship between thermospheric density perturbations in the altitude of410km and Sym-H index are analysed as well as the deviation of TIEGCM model. The results show that, the model can simulate well the trend of the density along orbit during geomagnetic storm; and at the same time with Sym-H index sharp declining, the model are generally lower than the measured one. Thermospheric density perturbation is linearly related to Sym-H index during geomagnetic storm, and the density increments at different latitude show different response to Sym-H index, and such response is more pronounced on the dayside. The model also can reflect the linear response of the atmospheric density perturbations to Sym-H index during geomagnetic storm. The deviation of TIEGCM model at high latitude is higher than at low latitude, and the deviation has an increasing trend when Dst index is decreasing, and when Dst index decreases below-150nT, absolute and relative deviation change little.