Evolution Character Analysis Of Total Solar Irradiance

The total solar irradiance (TSI) is the total solar electromagnetic energy flux over the wholespectrum which arrives at the top of the Earth’s atmosphere at the mean Sun-Earth distance, andit affects the total energy from the Sun into the Earth system. Energy from the Sun reaching theEarth drives almost every known physical and biological cycle in Earth system, and is the veryimportant source of energy. Before TSI was measured by Hickey-Frieden cavity radiometer (HF)on Nimbus7in October1978, because of the low precision of the ground-based instruments,people thought TSI was a constant, so it was called Solar Constant. After HF was launched intospace, there are usually2～4radiometers onboard spacecraft outside the Earth’s atmospherewhich measured TSI. Because these radiometers have measured TSI, people know that TSIvaries on all time scales, i.e. minutes to decades. TSI generates the Earth’s radiation environmentand influences its temperature and atmosphere, even small persistent variation of the solarirradiance takes part in climate changes, so it is very import for us to understand how thevariations of TSI affect the Earth’s climate system, and now there are many investigations,especially investigations which have considered how the TSI influences the Earth’s climate ofthe long time and the global worming problem. At the same time, the research of TSI hasimportant implications for our understanding of physical mechanism of the solar surface andinterior, Earth’s atmosphere, solar-terrestrial relationship, and so on. Space-based observationsare only from1978on, due to short duration of direct measurement of TSI; constructions of TSIon long time scales are of importance and needed. The constructions of TSI have made bigprogress, but have some shortages too, so we should know the physical mechanism of thevariations of TSI better.To begin with, we review the research of TSI, including the measurements of TSI,constructions of TSI, and evolution characters of TSI. Then, utilizing the continuous wavelettransform, cross wavelet transform and wavelet coherence, we analyze the relations of TSI withsunspot area and Mg II index. We find the solar quasi-rotation periods are difference in solarcycle23and24, and get the relations of TSI with these proxies.We analyze the relations of TSI, which are measured by Total Irradiance Monitor of SolarRadiation&Climate Experiment, with sunspot area and Mg II index, and found the significant periods of total solar irradiance are35and26days in solar cycle23and24, respectively, it isinferred that the solar quasi-rotation periods are35and26days in solar cycle23and24,respectively. The value of total solar irradiance in solar cycle24minimum should be close to thevalue of Maunder minimum. On short time scales, sunspots should be the main reason to causevariations of total solar irradiance on the scale of one solar rotation cycle to several months, butnot the unique one, and the variations of total solar irradiance are not related with Mg II index onthe scale of a few days to one solar rotation cycle. Composite TSI of ACRIM are utilized here toanalyze too, and find the variations of TSI are not relations with sunspot area and Mg index onthe scale of the Schwabe solar cycle.