Some fresh indications of the solar origin of 4-6-year oscillation of the Earth’s rotation parameters

Abstract

The variations of universal times difference UT1-TAI and Earth’s rotation instantaneous pôle coordinates (X,Y) are studied in the frequency range of 3 - 8 yr−1 as a function of the solar activity. It is found that power spectrum concentrations C1 and C2 are common to solar activity indicators and Earth’s rotation parameters (ERP). The linear correlation between them is also not a fortuitous one. Accordingly, by the results of this study the hypothesis of Djurovic and Pâquet (1996; 1999) that the primary cause of 4-6 year oscillation lies in solar irradiance is confirmed. Between several mechanisms responsible for the ERP variations as the most probable are considered the variations of solar irradiance spectral structure (especially large in its UV range) and variations of intensity of cosmic X-rays reaching the Earth’s surface.