Solar-rotational oscillation and its harmonics in the solar-wind, geomagnetic and cosmic ray particles during the last two solar minima

Abstract

The behavior of short-term oscillations (≤one solar rotation) of the solar-wind parameters, galactic cosmic rays and geomagnetic indices are discussed during the last two solar minima between cycles $22/23$ and cycles $23/24$. There are strong signatures of short-term oscillations of all the selected time series during the early phase of the minima, where the high speed streams are prominent structures in the heliosphere and these signatures almost die out at the end of the two minima. Result also suggests that the second and third harmonics of one solar rotation period of few parameters are prominent during the minimum between the cycles 22 and 23. Moreover, all the sub-harmonics/quasi-oscillations are more consistent and deviate less during the recent deep prolonged minimum. Through this work, we are reporting ∼7.1 days, ∼5.5 days, ∼4.4 days, ∼3.3 days oscillations, observed in few solar-wind parameters [interplanetary magnetic field $(B)$, RMS standard deviation in the magnetic field ($\sigma_{B}$), southward component of magnetic field $(\mathit{Bz})$ and electric field $(\mathit{Ey})$] and geomagnetic ($D_{\mathit{sT}}$ and $\mathit{AE}$) parameters during the solar minimum between cycles 23 and 24, in addition to ∼1.9 days oscillations which is observed in $\mathit{Bz}$, $\mathit{Ey}$ and $\mathit{AE}$ parameters.