Increase of onboard aircraft exposure level during a solar flare

An Si-diode spectrometer was used for long-term monitoring of the exposure level on board an CSA a.s. aircraft between 22 March and 7 May 2001. A rather intense solar flare was registered by a terrestrial cosmic radiation monitoring station on 15 April at 13:50 UTC, Ground Level Event (GLE) number 60. At that time, the aircraft with the above equipment onboard was on its flight from Prague to New York. After the end of the monitoring period, an increase in the onboard exposure level was identified in the record of measurements. The data which have been registered directly showed an increase by a factor of roughly two as compared to the galactic cosmic radiation solely, both in the pulse rate and in the dose rate absorbed in Si. The event spectra during the flare were also different from those obtained from the galactic radiation solely. Analysis suggests that the quality factor increased during the solar flare. The results of the tentative quantitative and qualitative analysis are presented and discussed. (author)