Signatures of thunderstorms in the variations of the secondary cosmic rays registered in Mexico City

We studied the effect of thunderstorms (TS) in the intensity variations of the electromagnetic and muon components of the Cosmic Rays during the year 2004, a year of minimum solar activity. We analyzed the variations in the counting rates of the upper and lower scintillators of the muon telescope installed in Mexico City at times of reported TS and compared those with variations during quiet times. The data were filtered to eliminate long trends, then a wavelet spectrum was calculated, searching for the temporal evolution of diverse periods of high significance; recurrent periodicities and total power distributions were obtained. The results show variations of short period whose main periodicities are arranged in a distribution where the most important are the shortest periodicities. These may be associated to the electric fields of the TS. Significant long period variations were found too, these could be due to other processes linked to rainstorms. No systematic effect on the power of variations due to TS was found.