Analyzing solar activity with Belgrade muon station: case study of 2021 November 4th Forbush decrease

The first significant Forbush decrease of the solar cycle 25 was recorded on November 4^th, 2021. The Forbush decrease was observed with numerous ground based cosmic rays stations including Belgrade cosmic rays muons' station. Series of coronal mass ejections during October 28-November 4 2021. produce conditions for this Forbush decrease. We discuss here the variation of cosmic rays' flux detected with ground-based detectors and connection with conditions, measured in-situ, in interplanetary space around Earth, flux of solar wind protons measured with SOHO probe to assess implication for solar-terrestrial coupling processes.