Galactic cosmic ray fluctuations during solar cycles 22 and 23 at high altitude neutron monitors Original Research Article

Cosmic ray detectors installed at high magnetic cutoff rigidity and mountain elevation are only a few. It is therefore important to have reliable data for active monitors with these characteristics. The Mexico City 6-NM64 has been in continuos operation since 1990. It is located at an altitude of 2274 m above sea level and has a vertical magnetic cutoff rigidity of 8.2 GV for the 1990 epoch (Shea and Smart, 1997). In this work we make a study of the cosmic ray intensity fluctuations observed in Mexico City and compare it with other mountain altitude neutron monitors of the american sector during the years 1990–1999. The period comprises the maximum and declining phase of solar cycle 22 and the beginning of cycle 23. Evolution of important variation periodicities compared with solar activity indicators are presented. We have also constructed a new solar activity index based on the measured hard x-rays flux.