The Study Of The Geomagnetic Storm Caused By CMEs

Coronal mass ejections(CMEs)are the main cause of magnetic storms.The CME spreads to the earth through the interplanetary space,which makes the earth's magnetic field severely disturbed in a short period of time and has a tremendous impact on human activities such as human spaceflight and satellite navigation,long-distance transmission and oil transmission networks,and geological exploration.Because of the great impact of magnetic storms on the national name economy and national security,it is very urgent to predict the occurrence of magnetic storms in advance so as to avoid the harm caused by magnetic storms.The transport time is defined as the interval time between the occurrence of CMEs and the maximum value of the geomagnetic storm.Using the 89 CMEs-Dst events collected from 1997 to 2015,we use the distant correlation to obtain the correlation values between CME speed,energy,flare type et and transit time.Then,Based on the correlation between each parameter and the CME transport time,we use non-linear fitting and support vector machine(SVM)nonlinear regression techniques to establish CF(Curve Fitting)model and Support Vector Machine(SVM)model based on 62 CMEs-Dst events from 1997 to 2009.The remaining 27 CMEs-Dst events were used to test the prediction effect of the two models and the ECA model established by Gopalswamy et al.The results show that:(1)The velocity parameters show near-linear correlation with the crossing time.When the speed is less than 1700kmls,the transport time decreases nearly linearly with the speed;when the speed is greater than 1700km/s,the transport time varies little with the speed;(2)The energy parameters show an exponential relationship with the transport time,and the transport time decreases exponentially with the increase of energy;(3)The flare type shows a near-linear relationship with the transport time.The transport time of CME is smaller with the increase of flare level;(4)The prediction accuracy rates of the CF model and the SVM model all reach 85.2%,and the accuracy of the ECA model is 77.8%.The model we built are both higher than the ECA model;(5)The average absolute value error of the CF model is 13.77h,while that of the SVM model is 13.88h,but the average absolute value error of the ECA model is 14.55h.The prediction error of the CF model is the smallest;(6)The CF model has the best prediction performance for large magnetic storms(-200<Dstmin?-100 nT)and extreme magnetic storms(Dstmin ?-200 nT),while the SVM model has the best prediction performance for medium magnetic storms(-100<Dstmin?-50 nT).It is possible to give a transport time indication of the geomagnetic storm explosion with 1-5 days in advance.