Solar wind plasma variations with interplanetary magnetic field during solar cycles 22-24

In this paper, we have studied the relationship between the monthly variations of solar wind plasma velocity, interplanetary magnetic field (IMF) and geomagnetic activity index (Ap) during solar cycles 22-24 (1986-2020). The modulation parameter (zeta = V * B) is proportional to the product of solar wind plasma velocity, V and strength of the interplanetary magnetic field, B. We have investigated the periodicities and their evolution during solar cycles 22-24 using Fast Fourier Transform (FFT), RobPer periodogram and Continuous Wavelet Transformation methods. The significant periods present in the modulation parameter include the Rieger type, semi-annual period, annual period and quasi-biennial period (mid-term). In this study, we have found that the rotation rate at the base of the convection zone is similar to 1.30 years. Quasi-biennial oscillations (QBOs) of solar wind plasma velocity, IMF, modulation parameters and Ap have been compared. The modulation parameter appears to be a better representative of the geomagnetic changes than the other two.