BEXCO - Room F(201/202/203/204)
[SH135] The extraction of GLE #5 from ionization chamber recordings
The ionization data of GLE #5 is extracted from the ionization chamber recordings of three stations, viz; Godhavn, Cheltenham, and Christchurch. To verify the accuracy of the extraction algorithm a synthetic ground truth image of historic cosmic ray ionization data recordings was first constructed from properties of the original image. It is not a perfect replica of the original but rather a similar image where only the properties of interest are accurately described. A synthetic version of the ground truth image, that to some degree, reproduced the distortions and optical artefacts present in the original image was then created. The detection algorithm was then applied to the synthetic image and the extracted values compared to the ground truth image to evaluate the detection capabilities of the algorithm, using measures such as MSE, precision, accuracy and recall. The ionization data of GLE #5 was then extracted from the ionization chamber recordings and converted to percentage increase above background cosmic ray levels, for comparison to existing neutron monitor data which was sourced from a GLE database. The percentage increase data was compared to that of neutron monitors from Leeds and Sacramento, as these locations offer insight into the range of GLE #5. The Leeds station is one of the stations with the smallest recorded percentage increase for GLE #5, whereas Sacramento has one of the highest recorded peaks for GLE #5. The important aspect of these comparisons is the general shape of the GLE, as the calibrations of the ionization chamber recorder are unknown. The images do share common attributes, and these include a sharp rise to a peak which tapers off more slowly. This trend is seen in all three data sets, and can be considered to be consistent with the existing (more accurate) neutron monitor data.