Atmospheric radiation boundary conditions for the Helmholtz equation Hélène Barucq, Juliette Chabassier, Marc Duruflé, Laurent Gizon and Michael Leguèbe ESAIM: M2AN, 52 3 (2018) 945-964 Published online: 13 September 2018 DOI: 10.1051/m2an/2017059