Abstract
Abstract. We analyse phase lags between the 11-year variations of three records: the semi-annual oscillation of the length of day (LOD), the solar activity (SA) and the cosmic ray intensity (CRI). The analysis was done for solar cycles 20–23. Observed relationships between LOD, CRI and SA are discussed separately for even and odd solar cycles. Phase lags were calculated using different methods (comparison of maximal points of cycles, maximal correlation coefficient, line of synchronization of cross-recurrence plots). We have found different phase lags between SA and CRI for even and odd solar cycles, confirming previous studies. The evolution of phase lags between SA and LOD as well as between CRI and LOD shows a positive trend with additional variations of phase lag values. For solar cycle 20, phase lags between SA and CRI, between SA and LOD, and between CRI and LOD were found to be negative. Overall, our study suggests that, if anything, the length of day could be influenced by solar irradiance rather than by cosmic rays.
Highlights
The velocity of the Earth’s rotation and the length of day (LOD) vary at different timescales from days to millennia (Rosen, 1993; Eubanks, 1993)
We present the results of our investigation based on the visual analysis and relationships of curve shapes and on the analysis of phase lags between sunspot number (SSN), cosmic ray intensity (CRI) and LOD for solar cycles 20–23
We have found minima of solar activity for the curves presented in Fig. 4 with a precision of about a month
Summary
The velocity of the Earth’s rotation and the length of day (LOD) vary at different timescales from days to millennia (Rosen, 1993; Eubanks, 1993) It is known since Starr (1948) that conservation of global angular momentum of the solid Earth–ocean–atmosphere system implies that a decrease in angular momentum of the fluid envelope is accompanied by an increase in the rotation rate of the Earth and a corresponding decrease in LOD. This is one of the reasons why the excitation of LOD variability has received such attention over the last decades, since the advent of the space era over which the accuracy of Earth measurements has increased dramatically (Eubanks, 1993; Gross, 2007). It is known that a large part of the lower frequencies, notably interannual timescales, is related to El Niño– Southern Oscillation (ENSO) phenomena (Hide and Dickey, 1991; Abarca del Rio et al, 2000) and with mantle–core coupling (Holme and de Viron, 2013), while at lower frequencies, even though the atmosphere–ocean coupled system may play a role, the greater part of the contribution is related to mantle–core coupling (Gross, 2007) effectively masking the geodetic signature of longer-term changes in the atmosphere–ocean system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
