A Study Of The Cycle Detection Of Solar Activity And Its Relation To The Ionospheric TEC Cycle

As the source of energy of the earth,the sun is the basis for maintaining all life on the earth.Solar activity is closely related to space weather and the Earth’s atmosphere.When the solar activity is strong,solar radiation will cause disturbances in the Earth’s ionosphere,which will lead to noise and interruptions in radio communications,affecting the lives and communications of people on the ground,especially affecting the performance of satellite communication systems and the operation of near-Earth satellites and space stations.The changes in solar activity also have an impact on the Earth’s climate.And the cyclical variation of solar activity is an important cause of space weather and Earth’s climate change.Therefore,the study of the cycle of solar activity,and the response of the total electron content(TEC)of the ionosphere to its variability,as well as the prediction of solar activity,has profound implications for both space science and geophysics.Based on this,the solar activity index,ionospheric TEC and geomagnetic activity parameters are selected in this paper.Firstly,the characteristics of the solar activity cycle are analyzed,and the solar activity cycle is detected by using wavelet decomposition and Fourier variation methods.Then,the overall variation relationship between solar and geomagnetic activity and ionospheric TEC,the characteristics of quasi-27-day periodic oscillations of the three at different stages,and the characteristics of the lag of TEC to solar activity are analyzed by using correlation analysis,Butterworth band-pass filtering,Fourier transform,and time-lag analysis.Finally,we compare the predictive power of the LSTM and SARIMA models and predict the characteristics of the 25 th solar activity cycle.The results show that:(1)A solar activity cycle lasts about 11 years.The duration of the rising period is generally shorter than the declining period.The larger the peak in sunspot number,the shorter the duration of the rising segment of this cycle,during each solar activity cycle.The sunspot maximum with a lag of two cycles is inversely proportional to the length of the time interval between the two maximum peaks.The rise time of each solar activity cycle is inversely proportional to the decline time.The maximum sunspot number is proportional to the rate of rise.The long periods of sunspot number occurrence are: 42.7,21.3,12.2,10.7,8.1,5.2,3.8,1.9 and 1.1 years.The short periods are 191.7,97.2,38.3,27.3,12.63,6.9 and 2.8 days.The amplitude of the cycle shows that the 10.7-year cycle corresponds to the largest amplitude in the long cycle.The 27.3-day period corresponds to the largest amplitude among the short periods.(2)TEC has a clear linear relationship with solar activity.The correlation coefficient |R|shows |R|EUV>|R|F10.7>|R|SN.while TEC does not have a significant linear relationship with geomagnetic activity parameters(|R|<0.35).TEC,the solar activity index and geomagnetic activity parameters all have a period of 3835 days(10.51 years).The spectral maxima of both TEC and the solar activity index are around 27 days.The spectral maxima of geomagnetic activity parameters are around 27 days and 13.5 days.The consistency of deviations from the quasi-27-day significant cyclic oscillations of TEC and the solar activity index.There is no significant relationship found between the quasi-27-day cycle of TEC and geomagnetic activity.The TEC lag time to F10.7 and EUV index is always consistent,and the lag time to sunspot number varies from phase to phase.(3)The predictive power of the LSTM model is better than that of the SARIMA model.We used the LSTM model to predict that the 25 th solar activity cycle will start in early 2020 and end in late 2029,with a 4-year rise and 6-year decline period,and the sunspot number peaking at the end of 2023 at about 156.8.