Morphology Analysis And Theoretical Study Of Global Ionospheric Disturbances During Magnetic Storm Times

Using the observed data obtained from stations all over the world and the related interplanetary and geomagnetic material, we study the response of global ionospheric F2-layer parameter NmF2 and hrnF2 to five typical different type geomagnetic disturbance events induced by different interplanetary magnetic cloud, by dividing the global ionosphere into high, middle and low latitude according the variations of magnetic latitude, and adopting the UT/LT(universal time /local time) method. It is shown that the ionospheric disturbances are obviously controlled by different interplanetary and storm conditions and that the disturbances are also very different for different latitude/longitude and universal/local time. The ionospheric storm reflects the complicated interaction between the interplanetary, magnetosphere, ionosphere and thermosphere during storm times. Besides 搕hermospheric storm circulation? there may exist other physical processes such as particle precipitation, top plasma fluxes, rnagnetospheric electric field penetration, disturbance dynamo electric fields, and neutral molecule excitation By improving and rebuilding the previous mid-latitude model, we extend the model to high latitude and low latitude, respectively. The extension to high latitude mainly includes the effects of convection electric field and particle precipitation. The low-latitude extension primarily takes account of the configuration of magnetic field and interliemispheric coupling. The model considers production, loss, and transportation of 7 ions including O~. The geomagnetic arid geographic poles is distinguished in our model. The time-dependent ion transport equations were numerically solved along fixed magnetic flux tubes. The lower boundary (100km) condition is set to chemical equilibrium. At mid-high latitudes, the magnetic field lines are assumed straight but inclined, and the plasma flux is set to zero at the upper boundary (800km). Allow latitude, magnetic field is assumed to be dipolar, and the upper boundary in fact is the other end of magnetic field hine(IOOkrn). In order to validate our model, we apply our model to space disturbance events occurred in April- May 1998 and mainly study high-latitude and low-latitude ionospheric responses. The comparison of simulation and observation shows that the model not only reproduces well diurnal change during magnetically quiet periods, but also can reflect the basic characteristics of ionospheric disturbance during magnetic storm times. Furthermore, we study the effects that a various of physical processes have on the high-latitude and low-latitude ionospheric disturbance during storm times. At high latitude, besides thermosphieric disturbances, we mainly study particle precipitation, convection electric field, neutral molecule excitation amid top plasma flux, which may affect the ionospheric F region disturbance. At low latitude, we primarily study thermospheric disturbance winds, disturbed neutral composition, disturbance dynamo electric fields and magnetospheric electric field penetration, which may have an effect on the appearance and development of equatorial anomaly.