Statistical analysis of the ionosphere response to the CIR and CME in Mid-latitude regions

Abstract

The study of the ionosphere responses to Corotating Interaction Regions(CIRs)and Coronal Mass Ejections(CMEs)got much attentions in rencent years.With the comparison of different types of ionosphere response caused by different disturbance sources from solar activity and interplanetary solar wind,morphological changes and physical process of ionospheric storms can be understood more impressively and comprehensively.It provides a possibility to predict ionospheric disturbance states according to different solar wind conditions in advance as well.GPS-TEC data at a mid-latitude station(131°E,35°N)are used to analyze the ionosphere response during geomagnetic disturbances induced by 109 CIRs and 45 CMEs over the period 2001 to 2009.Firstly,the TEC difference are determined to achieve the information of ionospheric positive or negative storms during the CIR and CME events.The definition of a ionosphericstorms is relative TEC greater than or equal to 15% and persisting for more than 4hours;Secondly,year dependence,seasonal dependence,time delay between ionospheric storms and geomagnetic storms,geomantic storm intensity dependence and time duration of ionospheric storms are analyzed in detail.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-6to 6hours in general,but CIR-driven ionopsheric storms involve in a wider range with a time delay of-12 to 24hours and CME-driven storms is delayed from-6to6 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.Our investigation also demonstrates certain correlation between the types of ionospheric storms and the AE maximum indices.Ionopsheric negative storms often occur in stronger geomagnetic activity,with the AE maximum intensity between 800 to 1200nT while positive-negative storms tend to occur with AE maximum intensity higher than 400 nT.Compared to CIR driven storms,AE maximum value during CME driven storms is higher.The duration of CIR-driven storms is longer(1to 6days)than that of CME-driven storms(1to 4days).The ionosphere response to interplanetary conditions contribute to the study the ionospheric disturbance.Statistical analysis of the ionosphere response to the CIR and CME in Mid-latitude regions indicate that there are some certain correlations among ionospheric changes,solar activities,interplanetary conditions and geomagnetic conditions.The ionospheric storms could be predicted more accurately and meticulously by distinguishing the different types of interplanetary conditions.