Speaker: Kasper van Dam, Nikhef
Cosmic rays are charged particles from space. If a cosmic ray hits the
Earth's atmosphere a cascade of secondary particles is created. Depending
on the energy of the primary particle this cascade can result in a
measurable footprint at ground level. The vast majority of cosmic rays are
not energetic enough and only single particles (mostly muons but also
electrons) reach the ground. The flux of these single atmospheric muons is
measured by many detection stations throughout the Netherlands and UK that
are part of the HiSPARC experiment. Several times per month we see a
temporary increase in this muon flux that lasts for typically an hour and
seems to move like a weather front across the country. The cause of the
temporary increase is unknown. Simulations of air showers show that a
local increase of the pressure in the atmosphere at ~15 km height by 30%
increases the count rate on the surface of the Earth by 30%. Also, there
seems to be a relation with thunder storms. In this talk I will quickly
introduce cosmic rays and HiSPARC, I will discuss the flux increases and
talk about some hypotheses we are researching to explain this phenomenon.
