HHS Cosmic Ray Muon Research-2016
The 2015-16 HHS AP Physics C E&M class analyzed data from the Muon detector at the University of Rochester. A muon is a fundamental particle that is essentially a more massive and less stable version of the electron. Muons are created by collisions of cosmic rays (high energy nuclei) with atmospheric molecules and can then be detected and counted by the U of R detector.
The graph above shows the effect on muon rate of the dramatic drop in barometric pressure during Hurricane Sandy in 2012. Since the atmosphere acts as a muon absorber, deceases in pressure increase the muon rate.
The graph above illustrates the anticorrelation between barometric pressure and muon rate (source: Grant Hevia).
The graph above plots the muon rate for the month of January 2015 (source: John Ceballos). The pronounced drop in rate early in the month was likely due to a moderate geomagnetic storm and/or a geo-effective coronal hole/increased solar wind speed during the 1st week of the month.
The graph above plots pressure-corrected muon data for 2015 through mid November (source: Ethan Makulec). There seems to be evidence of a long-term trend as the rate decreases through the summer. Also, there is a pronounced decrease on June 23rd due to a series of solar flares on June 21-22 and subsequent geomagnetic storm. This decrease is known as a Forbush decrease. This particular decrease is shown in more detail below with xray and k-index (an index scale of geomagnetic activity) graphs from the period.
Xray data showing flares on June 22-23 (source: NOAA).
Kp index showing geomagnetic storm on June 22-23 (source: NOAA).
Finally, the graph above plots pressure-corrected hourly rates that were averaged over an entire month (Dec, 2010). This month was chosen in part because this was a period of very little solar activity, which reduced the chance of other factors affecting the rates. The peak occurs at approximately 20:00 UTC (3:00 PM ET) while the lowest value occurs at roughly 10:00 UTC (5:00 AM). The variation is very small (<1%), but is significant relative to the uncertainty (.000164 Hz).