On the phenomenon of the blue sun:
Nellie Wullenweber,Anna Lange,Alexei Rozanov,and Christian von Savigny
“This study examines the cause of the blue colour of the sun as observed after the eruption of Krakatao in 1883 as well as other volcanic eruptions or massive forest fire events. Aerosol particles, e.g. volcanic ash or products of biomass burning, are believed to be able to modify the spectral distribution of transmitted solar radiation making it appear blue or green to a human observer.”
“We investigated possible reasons for the occurrence of a blue sun, including anomalous scattering by suitably sized aerosols, aerosol absorption, and absorption by water vapour and O3. This study included – for the first time to our best knowledge – a comprehensive treatment of Rayleigh scattering in simulations of a blue sun. Depending on the specific aerosol and observational parameters (SZA), Rayleigh scattering was found to have a significant impact on the simulated colour of the sun. Anomalous extinction is more pronounced for narrow aerosol particle size distributions (given the right aerosol size), but the investigations based on the aerosol optical depth retrieved by Wilson (1951) demonstrated that a relatively weak increase in aerosol extinction with wavelength in the visible spectral range also allows simulating a blue sun.”
More in depth information can be found here: https://cp.copernicus.org/articles/17/969/2021/
Incredible footage captured by PyramidCam, of the rare phenomenon called BLUE SUN.
