Cyclic variations in the solar differential rotation pattern based on the Hα filament data (1957–1993)

Abstract

Using polynomial regression models, we studied the differential rotation of the solar chromosphere $H_{\alpha }$ filaments on the basis of data from the Abastumani Astrophysical Observatory. Current research uses discrete orthogonal polynomials to examine how the solar differential rotation of the $H_{\alpha }$ filaments varies with solar cycles. For differential rotation regression models, we consider discrete orthogonal polynomials up to degree 4. When performing regression analysis, we apply the Akaike information criterion. Regression analysis of the $H_{\alpha }$ data indicates that the best fit for polynomial models of the solar differential rotation is achieved with discrete orthogonal polynomials of degree 2. The equatorial values of the rotation rates remain almost constant for the period 1957–1993, while the average angular velocity, the ”rigid body” rotation rate, has cyclic variation and a decreasing linear trend. The spatio-temporal distribution of rotation rates hints at a 22-year periodicity in the differential pattern of rotation of the Sun.