Study of the Solar Rotational Period and Its Harmonics in Solar Activity, Interplanetary, Geomagnetic, and Cosmic Ray Intensity Indicators During Solar Polarity Reversal Periods

Abstract

Short-term variations of interplanetary magnetic field, solar wind speed, solar radio flux, geomagnetic ap index and cosmic ray intensity have been studied during the last five polarity reversal periods in the period from Solar Cycles 20 to 24. Hourly data of all the considered parameters are subject to wavelet analysis exclusively during the polarity reversal periods of these five solar cycles. These solar polarity reversal periods lie during or around the solar maximum of the respective solar cycles. Study reveals a few noteworthy results during these disturbed periods. Periodicities such as the synodic period ( ${\approx\,}27.0$ days), its second ( ${\approx\,}13.5$ days) and third ( ${\approx\,}9.1$ -days) harmonics, ${\approx\,}6.8$ -day, ${\approx\,}5.5$ -day and ${\approx\,}4.2$ -day periods are consistently observed during the reversal times with prominent signatures in addition to quasi-periodicities (18.5 days, 16.7 days, 10.6 days, 2.8 days, 2.4 days, and 1.8 days). These significant variations are very strong during reversal periods as they appear in minimum phases of the solar cycles, as reported by Singh and Badruddin (Astrophys. Space Sci. 359, 60, 2015a); they could be the higher harmonics (fourth, fifth, and sixth) of the synodic period.