Tunneling of relativistic bosons induced by magnetic fields in the magnetar's crust

The present work is devoted to the study of bosons evolving in the frozen magnetar's crust endowed with an ultra-strong magnetic field orthogonal to an electric field, both described by periodic functions. We discuss the quantum tunneling process through the one-dimensional potential barrier along O_z. The solutions to the Klein-Gordon equation are expressed in terms of Mathieu's functions which, for computable particle's energy range, are turning from oscillatory to exponentially growing modes along O_z. Within the Jeffreys-Wentzel-Kramers-Brillouin framework, the transmission coefficient is computed for the particle momentum in the middle of the instability range. (authors)