Determination of short-period terms of total solar irradiance

Abstract

In addition to the evident 11-year periodic changes, Total solar irradiance (TSI) also has some short-period processes. We carried out the wavelet analysis for TSI observational series and its inter-annual time series that is filtered out components less than 2 years and more than 8 years . Whether the wavelet graph or the global wavelet power spectrum, the results significantly show that there is a short period about 5.3 years, and its length and intensity both vary with time. Specifically, the strength of this period varies with the 11-year cycle change, showing pronounced characteristics of peak strength and valley weakness. Moreover, the amplitude of these low-frequency fraction results indicates different TSI variation properties. Under each solar cycle, the sum of the power spectrum density of the 3–6 year period terms reflects that the energy value of the short period is concentrated in that range. When the 11-year cycle is intensive, the 3–6 year period also becomes intensive in TSI. And the total spectral intensity of TSI will be concentrated in that short-period terms.