Solar Eclipse and Cosmic Ray Flux

During the August 21, 2017, solar eclipse, high school students measured secondary cosmic ray flux using QuarkNet detectors. These students conducted experiments examining cosmic ray flux, shower, speed of muons, and muon lifetime using QuarkNet cosmic ray muon detectors (CRMDs). These detectors measure muon flux of momenta greater than ~2 GeV, a threshold imposed by deflection due to Earth’s magnetic field. This study utilized CRMDs, which are readily available for students, to investigate any deviation in secondary cosmic ray flux resulting from a solar eclipse. Other groups have conducted experiments regarding cosmic rays during eclipses: Kandemir et al. reported on low-energy muons (under 1 GeV) during the eclipse of August 11, 1999; Nayak et al. and Bhaskar et al. studied air showers for gamma ray point sources; and Nishina et al. studied muon flux during a 1936 eclipse. Cosmic rays are charged particles created in exploding stars and active galaxies and travel through interplanetary space at relativistic velocities. The flux is largely unchanged between day and night, when Earth blocks the Sun, and the presence of the Sun and Moon has little effect. A total eclipse provides a dramatic opportunity to search for that fraction of cosmic rays created by the Sun that are intercepted by the Moon. We hypothesized that muon flux will change during a total solar eclipse; however, we designed the experiment to search for signals at various angular scales near the direction of the Sun and to set upper limits on production from the Sun if no signal was observed.