The virtual enhancements − solar proton event radiation (VESPER) modelSigiava Aminalragia-Giamini, Ingmar Sandberg, Constantinos Papadimitriou, Ioannis A. Daglis and Piers JiggensJ. Space Weather Space Clim., 8 (2018) A06DOI: https://doi.org/10.1051/swsc/2017040