A possible effect of the atmospheric transparency decrease, caused by solar cosmic rays, is investigated. The data of transparency measurements on the high and mid-latitude stations: Murmansk, Archangelsk, Leningrad have shown that the effect really took place in a number of events with great intensity of solar protons. Two to four times the number of density increase of the big aerosol particles was observed in all these cases. So the obvious cause of the transparency decrease is an attenuation by the aerosols generated by the energetic solar particles.
V. C. Roldugin,
Eduard V. Vashenyuk,
"Reduction of atmospheric transparency by solar flare protons", Proc. SPIE 2049, Atmospheric Radiation, (2 November 1993); doi: 10.1117/12.163536; https://doi.org/10.1117/12.163536