Abstract

The effect of storm onset time on the ionospheric response to the initial phase of the storms has been studied using both ground-based GPS TEC data and Coupled Magnetosphere Ionosphere Thermosphere (CMIT) model simulations. The CMIT model captured most of the observed ionospheric responses includ... Show moreThe effect of storm onset time on the ionospheric response to the initial phase of the storms has been studied using both ground-based GPS TEC data and Coupled Magnetosphere Ionosphere Thermosphere (CMIT) model simulations. The CMIT model captured most of the observed ionospheric responses including the daytime positive response in low and middle latitudes and the negative response along the geomagnetic equator. These ionospheric responses are the results of penetration electric fields. Three CMIT simulations are carried out with the same solar wind/IMF conditions but the storm onset times are separated by 6 hours. For all three model simulations the ionospheric responses are similar. However, there are significant differences in the magnitude and morphology of these responses for different storm onset times. Further analysis shows that the pre-storm background ionospheric conditions and the magnetic field configuration are the two most important factors that cause differences in penetration electric fields when the storm onset times are different and thus differences in ionospheric responses. Show less