The interconnection and phase asynchrony between the geomagnetic indices’ periodicities: A study based on the interplanetary magnetic field polarities 1967–2018 utilizing a cross wavelet analysis

In this article, we investigate the interconnection and phase asynchrony between periodicities of geomagnetic activity indices Kp , Ap aa Dst according to interplanetary magnetic field (IMF) polarities, toward ( T ) or away A ), during time interval 1967–2018. For purpose, daily data Ap, considered period have been sorted into two groups IMF polarities. The wavelet transform (WT), cross-wavelet (XWT), coherence (WTC) applied on monthly averages for each index. Moreover, correlation analyses (linear running correlations) annual index investigated. results XWT WTC revealed existence a long-term periodicity in frequency range 8–16 yr existed entire period. contrast, 1980–2018. addition, band, both highly positive nearly in-phase relationship behavior. Furthermore, band 4–8 yr, displayed prominent that occurred index, revealing change some intervals. Periodicity 2–4 intervals; 1967–2009 1967–2007 1976–1995 . is also identified all indices. Both shared semiannual (~187 days) different intervals On other hand, around 0.25-yr (~90 appeared only near times solar maxima case