Statistical Analysis Of The Ionosphere Response To The CIR And CME

Ionospheric response to geomagnetic storms varies complexly with solar activity, season, time and space. The forecast of ionospheric disturbance is still an unresolved problem in current space weather. This paper focuses on the distinction at different interplanetary conditions which can cause geomagnetic storm(Corotating interaction regions, CIRs and Coronal Mass Ejections, CMEs), and analyzes the similarities and differences of the characteristic of ionospheric disturbances caused by these two interplanetary sources. The simulation results of a theoretical model are used to analyze cases, investigating physical mechanism which may cause ionospheric disturbances. The main contents and results of this paper are as follows:GPS-TEC data at a mid-low latitude lattice(131oE, 35oN) are used to analyze the ionospheric response during geomagnetic disturbances induced by 109 Corotating interaction regions(CIRs) and 45 Coronal Mass Ejections(CMEs) over the period 2001~2009. Analysis results indicate that the types of ionospheric storms vary in different phases of a solar cycle. CIR-driven positive and positive-negative storms are more likely to occur in the declining phase of the solar cycle, while negative phase storms more in solar maximum and negative-positive storms mainly in solar minimum. CME-driven positive storms and negative storms mostly occur in solar maximum. There is no remarkable seasonal difference for the occurrence of different types of ionospheric storms except the positive-negative storms most likely to occur in summer. The time delays between geomagnetic disturbances and the start time of ionospheric storms are-6~6 hours in general, but CIR-driven ionopsheric storms involve in a wider range with a time delay of 12~24 hours and CME-driven storms is delayed from 0~6 hours. Moreover, for CIR-driven ionospheric storms, positive and negative storms mostly occur in main phase of magnetic storms, positive-negative storms mostly in initial and main phase, and negative-positive storms mainly in initial phase. For CME-driven storms, positive, negative and positive- negative storms basically occur in main phase. Ionopsheric negative storms often happen in stronger geomagnetic activity, with the AE maximum intensity between 800~1200n T. The duration of CIR-driven storms is longer(1~6 days) than that of CME-driven storms(1~4 days).GPS-TEC data at a mid-high latitude station(105.3oW, 40oN) are used to analyze the ionospheric response during geomagnetic disturbances induced by 68 CIRs and 53 CMEs over the period 2001~2009. Ionospheric disturbances in Boulder station are similar to that in Japan, while there are some differences between the two stations. CME-driven negative storms in mid-high latitudes are more obvious than in the mid-low latitudes. Negative-positive storms occur in mid-high latitudes less than in mid-low latitudes. The seasonal effect of ionospheric storms is related to the latitude, and in mid-high latitudes winter is inclined to occur positive storms and summer to occur negative storms. Time duration of positive storms in mid-high latitudes is shorter than in mid-low latitudes.TEC measured data and the simulation results of TIEGCM mode are used to analyze ionospheric storms driven by CIR on third of April 2005. In the same longitude belt, positive storms can be first observed at high-latitude stations in the northern hemisphere. The lower latitude is, the longer time delays. Besides ionospheric storms are mostly positive-negative storms at high latitudes in the CIR-driven storm, and at low latitudes in the Americas and Asia, multi-day positive storms can be observed. TIEGCM mode is in good correspondence with measured data, reflecting consistent positive and negative storm effects with measured data. But the mode underestimates TEC, and deviation is smaller in the dayside than in the night in mid-low latitudes. Positive effects relate to increased O/N2 in low-mid-high latitudes; and in the daytime electric field penetration is also the important reason of positive effect. In low latitude region days of positive effects are mainly associated with increased O/N2 during the recovery phase.