Muon Flux Counts from St. Croix, U.S. Virgin Islands

Showing Selected Periods from 081109 to 072514


James A. Petrait


These muon observations were made at selected times when the computer and monitor could be kept on for longer lengths of time. During the selected time periods, the observations were divided into day long periods as much as possible. However the starting and end times may vary and parts of some days may be missing because of power failures. The correct starting times are indicated on the graphs. Adjust the graph time axis by adding or subtracting an hour if there is any difference. The graph shows time versus the average count per minute (expressed in microroentgens per minute) for 60 minute periods. The counts per minute are almost the same as microroentgens per minute and differ by a ratio of 100:105.

The location on the island of St. Croix is near 17.7 degrees North Latitude and -64.8 degrees West Latitude at an elevation of around 30 meters. All the times on the graphs are Atlantic Standard Time (AST) which is -4 hours from GMT.

The method used to detect the muons is described in my online article Monitoring Muons on the Surface of the Earth . For these observations, the coincidence detector was placed straight up at a 180 degrees.

Muons are secondary particles and arrive at the measuring instrument as part of a background flux which varies randomly, but over longer periods of time the data can be analyzed for meaningful variations with sunspots which can be observed at the Very Latest SOHO Images and other variables which are located at Today's Space Weather. The Satellite Environment Plot and its Kp index graph at the Space Weather site looks that it may show the effects of the primary particles deflections due to the change in the magnetic field of the earth. Most of the high energy primary particle are deflected towards the poles of the earth. However, there are anomilies like the one in South America where some of the the primary particles may enter. Also some of the primary particles may not have a charge and can pass directly down and generate secondary muons.

I am still analyzing the data but there is possibly a higher average muon count when some sunspots are present on the sun. During night time, any high energy partcles from the sun would have to pass through the earth so many of the primary high energy particles would be arriving from other points in outer space. The high energy particles from outer space also occur in the daytime in addition to the high energy particles from the sun.

Experimenters who are viewers of this website or those who like to analyze data are welcome to see if there is anything meaningful in these observations or from their own observations. Besides my own interest in the subject, I hope the posting of the data from my observations will encourage others to participate in this research.


Go to the Graphs of the Observations:


Muon Flux Data from St. Croix, U.S.V.I. during July, 2014


Four Day Muon Flux Count from St. Croix, U.S.V.I. from 012312 to 012712 Shows an Increase during the Solar Storm


Muon Flux Count from St. Croix, U.S.V.I from 033110 and 040110 Compared to 033111 and 040111


072210 to 072510


071810 to 072110


071410 to 071710


071110 to 071310


063010 to 070310


081109 to 081609


123010 to 011010


033110 to 040910


Return to Muon Flux Background Intensity Research


See more about muons and other science articles at the

Science Websites of James A. Petrait


For your convenience here is a list of conversion units:

CPM = microroentgens (µR) per minute (after a slight correction factor)

1 µR = 1 microroentgen = 1/millionth of a roentgen

1 microroentgens (µR) = 0.01 microsievert (µSv)

1 microsievert (µSv) = 100 microroentgens (µR)


© 2010 - 2014, James A. Petrait