Wavelet Analysis of 27-day Variation in Cosmic Ray Inten- sities Observed at Beijing Neutron Monitor

The paper analyzes the time variations of amplitude and phase of 27-day periodicity in cosmic ray (CR) time series observed at Beijing neutron monitor (NM) station and compares with those of geomagnetic parameter Ap series, using the Morlet Wavelet for decomposition. The results show that the amplitude and initial phase are all the function of time.