Research And Modeling Of The NmF2 Characteristics Of The Polar Ionosphere Under Geomagnetic Disturbance Conditions

The ionosphere is an important region for energy transmission and dissipation in the solar earth coupling system,which has a significant impact on radio communication and other related fields.The explosive activity of the sun can cause geomagnetic disturbances,trigger special events such as geomagnetic storms and substorms,and cause disturbances to the ionosphere,especially in the polar ionosphere,where the performance first appears and is most pronounced.With the increasing frequency of human activities in the polar region and the complex spatial environment in the polar region,it is crucial to study the changes in the ionosphere Nm F2 under geomagnetic disturbance conditions and conduct corresponding modeling and prediction research.This article focuses on the controversial issue of the causes of the peak daily variation of the polar ionosphere.Using Nm F2 observation data from Tromso,Longyearbyen,and Zhongshan stations in the Arctic for approximately one solar activity cycle,a combination of statistical analysis and event analysis is used to study and analyze the variation characteristics of Nm F2 in the polar ionosphere under geomagnetic disturbances from different perspectives.The impact of geomagnetic disturbances on the characteristics of Nm F2 variation in the polar ionosphere is studied,Further analysis was conducted on the main causes of the daily variation peak of Nm F2 in the polar ionosphere.In response to the lack of modeling in the polar ionosphere under geomagnetic disturbance conditions and the large prediction error of the IRI-2016 model in the polar region,based on the theoretical support in feature research,a representative characteristic parameter was selected to establish a combined model for predicting Nm F2 geomagnetic disturbance in the polar ionosphere,and a comparative analysis was conducted with the IRI-2016 empirical model.The main research work of the paper is as follows:(1)Statistical analysis was conducted on the daily variation characteristics of the ionospheric Nm F2 in polar regions during different solar activities and seasons under different geomagnetic disturbance conditions.In most seasons of high solar activity,the daily Nm F2 during geomagnetic calm is higher than that during geomagnetic disturbances,and the seasonal differences are not significant;Different geomagnetic disturbance conditions have no effect on the timing of the daily peak of Nm F2 in the polar ionosphere;Under the condition of geomagnetic disturbance,there are Nm F2 peaks on the night side of ZHS station in spring,LYB station in autumn and winter in the solar activity high year,which may be affected by the auroral substorm.The particle sedimentation causes the rise of electron density,leading to the emergence of the Nm F2 peak on the night side.(2)Based on a moderate intensity geomagnetic storm event,event analysis was conducted to compare the variation characteristics of Nm F2 in the polar ionosphere under different geomagnetic disturbance conditions during the initial,main,and recovery phases.The impact of different geomagnetic disturbances on the daily variation peak of Nm F2 in the polar ionosphere was analyzed,revealing the main cause of the night side Nm F2 peak at the latitude LYB station in the polar gap during the initial phase of the geomagnetic storm.(3)A combined model PLPR for predicting polar ionospheric Nm F2 was established by inputting relevant characteristic parameters under geomagnetic disturbance conditions.The prediction performance of PLPR model for polar ionospheric Nm F2 was evaluated from two perspectives: single prediction relative deviation analysis and overall error analysis.The reasons for the difference in Nm F2 prediction results between TRO and ZHS stations under geomagnetic disturbance conditions were analyzed,and a comparative study was conducted with the IRI-2016 empirical model,This provides reference opinions for improving and optimizing the applicability of the IRI-2016 empirical model for predicting the Nm F2 of the polar ionosphere under geomagnetic disturbance conditions.