How Much Did the 20 March 2015 Solar Eclipse Affect Cosmic Radiation Levels?

On the 20 March 2015, a solar eclipse of very high totality (greater than 90%) occurred across the UK. Data was taken simultaneously across the country and sent back to be analysed. Approximately twenty different centres collected data with a total of over 8000 frames being collected. In this project, the results from this data are analysed and then interpreted. They suggest a maximum decrease in background radiation levels of 46.3% about 70 minutes after the time of maximum totality (about the time of last contact). This project then concludes with a discussion of the possible implications and explanation of these results and an evaluation of the effectiveness and success of the experiment. 1 A Background to the Experiment Cosmic rays, as the name suggests, are rays of ionising radiation which originated from space (rather than on the Earth). Our atmosphere protects us from the most dangerous types of radiation, such as heavy ion fragments, causing them to split into alpha, beta and gamma radiation by the time they reach the Earth’s surface. Cosmic rays have many different sources with the Sun being an important factor but neutron stars, pulsars and other stellar bodies contributing as well. As part of an extended research project over several years, I have been studying cosmic rays and how they vary in intensity in different areas of the UK. Over twenty schools across the country are part of our research group and possess a Medipix 2 detector. The detector uses a silicon chip to record ionising radiation in a grid of 256x256 pixels to create an image of radiation, allowing different particles, alpha, beta and gamma, to be identified. On the 20 March 2015, a partial solar eclipse covered the whole of the UK with some regions of Scotland experiencing up to 95% totality. This was a rare opportunity to study such an event with our network of detectors across the UK. Radiation levels were measured using a standard method developed for the eclipse with each centre collecting two hours of data, approximately one hour before until one after the maximum totality of the eclipse. Data was then uploaded to our analysis site (http://starserver.thelangton.org.uk/analysis) where it was processed using a set of algorithms developed for analysing Medipix and Timepix data. I wrote two short programs in Python 3 to first convert the records of each frame which were stored on a database from the analysis program to a .csv file which could be downloaded for further analysis. Throughout the analysis, I used standardised times with time = 0 being the point of maximum totality. This allowed results to be directly compared as the time of maximum totality varied by almost ten minutes across the country which would have created a disparity between data sets. I then made a program that went through each .csv file, which corresponded to each upload of data, and used a dictionary to find first the sum and then find an average count rate for each relative second within three hours of maximum totality. I then used Excel to plot this data on a graph. The source code is included in an appendix.