The Study Of Ionosphere Disturbances During Geomagnetic Storm And Tropical Cyclone Based On New Ionospheric Indices

Because of severe factors which impose impacts on the ionosphere, such as solar activities, solar wind, interplanetary space, magnetosphere and lower atmosphere, the variation of ionosphere has many characteristics of various kinds, different parameters, complex sources, and very wide spectrum. Ionospheric disturbances are described from the perspective of the physical mechanism by using various ionospheric parameters(height, critical frequency, electron density, the component concentration, etc.). It is usually only for a single or a few events to analyze and classify, and it is difficult to make a statistically quantitative description of the ionospheric disturbances. Therefore, it is essential to have an ionospheric index, which is a simple numerical index and not dependent on physical process, to simplify the complex ionospheric phenomena. The construction of ionospheric index is an important direction of the ionospheric application research. It is of great significance to monitor and predict the ionospheric weather by processing the complex ionospheric disturbances into quantitative expression of the ionospheric index.This paper referenced the construction of ionospheric Js and Jp index in researches of Wang et al and Chen et al., and defined Jr index to reflect the ionospheric disturbances in different latitude.Total Electron Content(TEC) data from 2011 to 2014 processed by International GPS Service(IGS) is selected and processed into Js, Jr and Jp Index. The three indices were compared with Dst index during this time. The level of geomagnetic storm was divided by Dst index into weak, moderate and strong. According to statistics of different levels of geomagnetic storm during different Jp range, Jp index was negatively correlated with Dst index in general. The correlation coefficient between Js index and Dst index, from 2011 to 2014, reached-0.65 if Js is greater than or equal to the value 2. And the correlation coefficient reached-0.75 if Js is greater than or equal to the value 3.In order to fully reveal the three indices during geomagnetic storm, a geomagnetic storm in March 2015 is selected to analyze. Js were raised during geomagnetic storm. Js map well reflected the 2D ionospheric disturbances. The largest disturbance area moved from polar extended to the low latitude area and from east to west with the movement of the sun point. Jr and Dst had a similar variation trend. Different latitude of ionosphere was disturbed at different time respond to geomagnetic storm, and the response existed a noticeable delay. Jp showed a negative correlation with Dst, and the correlation coefficient reaches-0.72 around the geomagnetic activities from March 16 to 19.In order to verify the applicability of the ionospheric index to weak disturbance, this paper also analyzed the ionospheric disturbances during tropical cyclone. Based on regional high spatial and temporal resolutions of the TEC data, this paper analyzed the ionospheric disturbances during tropical cyclone Usagi. The 2D ionospheric disturbances were extracted and revealed by Js map. By comparing the Js map and TEC map, Js map during and before typhoon period, Js map under different typhoon intensities, it is showed a strong connection between the larger Js value area and TC track. In addition, the stronger TC is, the stronger disturbances will be produced.