Authors: A. Mubashir(GSU), A. Ashok(GSU), E. H. Mudiyanselage(GSU), E. Potdevin(GSU), T. Hettiarachchi(GSU), V. M. Sadykov(GSU), X. He(GSU)

The severe geomagnetic storm of May 2024 where the disturbance storm time index Dst reached a peak of 412nT was particularly significant for cosmic ray researchers, as it resulted in Forbush decrease detected by cosmic ray detectors, highlighting how geomagnetic disturbances affect cosmic ray activity. In the present study, we collected data from four detectors, including two GSU-developed muon telescopes and two neutron monitors installed at different cut-off rigidities. After applying atmospheric pressure and temperature corrections on cosmic ray data,  flux percentage change values were analyzed during heightened solar activity including the historic G5 event of May 2024 and G4 event of March 2024.  During these intervals, all detectors showed a notable correlation with each other and a time lag of two hours between the neutron and muon detectors for the highest cross-correlation, while a one-hour time lag was observed between the muon detectors themselves. A substantial decrease in flux before and during the two geomagnetic storms (G4 and G5) calculated as transient rates of flux change over intervals of ±3 hours, ±6 hours, and ±12 hours showed the most pronounced decrease occurring within the ±6 hour window. The cross-correlation time lag calculation between cosmic rays and geomagnetic activity, as well as solar wind parameters during the period from February to May 2024, indicates an estimated time lag of 2-3 hours between cosmic ray and Dst, and 2-4 hours for the solar wind speed. Additionally, the cross-correlation analysis between cosmic ray variability taken as the difference in cosmic ray between consecutive time steps and Dst in a time window of before and during geomagnetic storm suggests a delay of Dst by 5-10 hours.