Assessment of the radiation risk at flight altitudes for an extreme solar particle storm of 774 AD

Intense solar activity can lead to an acceleration of energetic particles and accordingly in crease the complex radiation field at commercial aviation flight altitudes. We considered here strongest ever observed event, namely that 774 AD registered on basis cosmogenic isotope measurements, computed ambient dose altitude(s). Since spectrum protons during event not be directly obtained, as a first step, we derived spectra GLE #5, by direct which was subsequently scaled size eventually used input corresponding model. The #5 conservative approach because it revealed hardest-ever energy spectrum. global map under realistic data-based reconstruction geomagnetic epoch, based paleomagnetic measurements. A #45 also considered, is scaling with softer lower particle fluxes compared GLE#5. altitude dependence integrated altitudes from 30 kft 50 for both scenarios. presented study effects extreme give necessary reference assess worst-case scenario specific threat,