| Total Solar Irradiance(TSI)is also called the "solar constant",but it is not a constant.It refers to the sum of the energy of solar electromagnetic irradiance in all bands that reach the top of the earth’s atmosphere per unit area per unit time at the average distance between the sun and the earth.and this total energy drives almost all known natural phenomena and biosphere cycles within our earth system;It is also the main driving force of the earth’s climate,and its relatively stable change within a certain range is also a necessary condition for the existence of human civilization.The change of total solar irradiance is a basic feature of the sun itself,which is closely related to sunspots,facula and other solar activities,which largely determines the relationship between sun-earth space and the structure of the earth’s high-altitude atmosphere.At present,the research content of total solar irradiance mainly includes three parts: data observation,periodic analysis,and reconstruction.For the periodic variation of total solar irradiance,scholars have found that the evolution of total solar irradiance shows similar periodic characteristics as the solar magnetic field activity,and is also modulated by the solar magnetic field activity.However,due to the different analysis methods used and the data used,the results obtained are different.The research content of this paper mainly includes the following three parts:First,this paper performs a simple statistical description and analysis of the observation data of daily total solar irradiance from November 17,1978 ~ December 5,2021 and sunspot data in the same time period,which contains 15725 pieces of data for about four solar cycles.Second,the continuous wavelet transform method is used to analyze the periodic variation law of total solar irradiance.The results show it has the characteristics of evolution of multiple periodic scales,and there are two statistically significant periods of 14.2 days and 31.7 days on the small-scale period(less than 64 days).It is believed that 31.7 days are the rotation period of total solar irradiance,and through regression analysis of the extracted rotation period series,it is found that the rotation period of total solar radiation shows a decreasing trend overall,from 29.79 days to 28.19 days in the considered time range.The components of the total solar irradiance signal were analyzed by empirical mode decomposition(EMD)method,and the original signal was divided into three components according to the periodic characteristics,namely rotation signal,annual change signal and solar activity cycle signal.Third,the relationship between total solar irradiance and sunspots was studied by cross-wavelet transform.The results show that the phase difference between the two is almost zero in the range of about 8~11.4 years.In the high-frequency part,whether it is total solar irradiance or sunspot number,both of which only show an oscillation period in the range of February ~ June,and are intermittently occurring near the maximum period of each solar cycle,and the phase relationship between the two is unstable.Therefore,compared with sunspots and spot brightening effects in this frequency band,the total solar radiation change plays a dominant role.Through the above analysis,we obtain the following main conclusions:(1)On the small-scale period,the statistically significant periods of total solar irradiance are 14.2days and 31.7 days.(2)From 1978 to 2021,the rotation period of total solar irradiance shows a decreasing trend.(3)The crossed wavelet transform(XWT)of total solar irradiance and sunspot number(SN)shows that they have oscillation period in the time range around the Schwab cycle(about 11 years),and the two time series are in phase;In the high-frequency part,the period in the range of about 2~6 months passed the significance test,and the strong power spectrum only appeared near the maximum of each solar cycle;The phase relationship between the two varies greatly with time,and the arrow distribution direction is almost random. |
PDF Full Text Request