Three-dimensional modeling of the Ca II H and K lines in the solar atmosphere Johan P. Bjørgen, Andrii V. Sukhorukov, Jorrit Leenaarts, Mats Carlsson, Jaime de la Cruz Rodríguez, Göran B. Scharmer and Viggo H. Hansteen A&A, 611 (2018) A62 Published online: 27 March 2018 DOI: 10.1051/0004-6361/201731926