  In this study we compared the temporal and periodic variations of the Maximum
CME Speed Index (MCMESI) and the number of different class (C, M, and X) solar
X-Ray flares for the last two solar cycles (Cycle 23 and 24). To obtain the
correlation between the MCMESI and solar flare numbers the cross correlation
analysis was applied to monthly data sets. Also to investigate the periodic
behavior of all data sets the Multi Taper Method (MTM) and the Morlet wavelet
analysis method were performed with daily data from 2009 to 2018. To evaluate
our wavelet analysis Cross Wavelet Transform (XWT) and Wavelet Transform
Coherence (WTC) methods were performed. Causal relationships between datasets
were further examined by Convergence Cross Mapping (CCM) method. In results of
our analysis we found followings; 1) The C class X-Ray flare numbers increased
about 16 % during the solar cycle 24 compared to cycle 23, while all other data
sets decreased; the MCMESI decreased about 16 % and the number of M and X class
flares decreased about 32 %. 2) All the X-Ray solar flare classes show
remarkable positive correlation with the MCMESI. While the correlation between
the MCMESI and C class flares comes from the general solar cycle trend, it
mainly results from the fluctuations in the data in case of the X class flares.
3) In general, all class flare numbers and the MCMESI show similar periodic
behavior. 4) The 546 days periodicity detected in the MCMESI may not be of
solar origin or at least the solar flares are not the source of this
periodicity. 5) C and M Class solar flares have a stronger causative effect on
the MCMESI compared to X class solar flares. However the only bidirectional
causal relationship is obtained between the MCMESI and C class flare numbers.

Solar and Stellar Astrophysics;Space Physics