Periodicities in solar coronal mass ejections

Mid‐term quasi‐periodicities in solar coronal mass ejections (CMEs) during the most recent solar maximum cycle 23 are reported here for the first time using the four‐year data (1999 February 5 to 2003 February 10) of the Large Angle Spectrometric Coronagraph on board the Solar and Heliospheric Observatory . In parallel, mid‐term quasi‐periodicities in solar X‐ray flares (class >M5.0) from the Geosynchronous Operational Environment Satellites and in daily averages of Ap index for geomagnetic disturbances from the World Data Center at the International Association for Geomagnetism and Aeronomy are also examined for the same four‐year time‐span. By Fourier power spectral analyses, the CME data appear to contain significant power peaks at periods of ∼358 ± 38, ∼272 ± 26, ∼196 ± 13 d and so forth, while, except for the ∼259 ± 24 d period, X‐ray solar flares of class ≳M5.0 show the familiar Rieger‐type quasi‐periods at ∼157 ± 11, ∼122 ± 5, ∼98 ± 3 d and shorter ones down to ∼34 ± 0.5 d . In the data of daily averages of Ap index, the two significant peaks at periods ∼273 ± 26 and ∼187 ± 12 d (the latter is most prominent) could imply that CMEs (periods at ∼272 ± 26 and ∼196 ± 13 d ) may be proportionally correlated with quasi‐periodic geomagnetic storm disturbances. At the speculative level, the ∼138 ± 6 d period might imply that X‐ray flares of class ≳M5.0 (period at ∼157 ± 11 d ) drive certain types of geomagnetic disturbances; the ∼28 ± 0.2 d periodicity is most likely caused by recurrent high‐speed solar winds at the Earth's magnetosphere. For the same three data sets, we further perform Morlet wavelet analysis to derive period–time contours and identify wavelet power peaks and time‐scales at the 99 per cent confidence level for comparisons. Several conceptual aspects of possible equatorially trapped Rossby‐type waves at and beneath the solar photosphere are discussed.