Abstract
Short-and mid-term oscillations of the solar activity (sunspot number and 10.7cm solar flux), geomagnetic activity (Ap index) and cosmic-ray intensity (neutron monitor count rate) are analysed during the past two solar-magnetic cycles (1968–1989 and 1989–2014). We have implemented the wavelet analysis on the daily time resolution data of sunspot number (SSN), 10.7cm solar flux, geomagnetic Ap index and Oulu neutron monitor count rate. Results suggest that few quasi and intermittent oscillations are observed with remarkable power density in addition to fundamental periods, like 27day (synodic period), 154day (Rieger period), semi-annual, annual, 1.3 year, and 1.7 year. We have consistently observed first (27day), second (13.5day) and third (9.0day) solar-rotation harmonics in the geomagnetic Ap-index during both the magnetic cycles. Rieger period is more pronounced in SSN and solar flux during 1980-82 and 1990-92. Semi-annual variation of Ap-index is consistently observed during both the magnetic cycles. The annual and ~1.85 year variation are also observed in all the considered parameters with good signatures in CRI.
•Wavelet analysis has been conducted to study short- and mid-term oscillations of the sunspot number, solar radio flux (10.7cm), cosmic ray data (Oulu neutron monitor during last two magnetic cycles).•The sub harmonics of 27 days period both on the lower (13.5 days and 9.0 days) and higher (51 days, 76 days and 101 days) side are present in the Ap index.•Solar maximum period and decreasing phases of the solar cycles are more appropriate to study short- and mid-terms variations.•The observed mid-term variations ~1.3 year and ~1.7 year are integral multiples of Rieger period. Hence, 1.3 year variation is first and Rieger period be fourth harmonics of fundamental period ~1.7 year. Moreover, there is mixing of these observed mid-terms oscillations of the time series.