  We analyze mesons in constant magnetic fields ($B$) within a non-relativistic
constituent quark model. Our quark model contains a harmonic oscillator type
confining potential at the leading order, and we perturbatively add short range
correlations to account for spin-flavor energy splittings. We study both
neutral and charged mesons taking into account the internal quark dynamics. The
neutral states are labelled by two-dimensional momenta for magnetic
translations, while the charged states by two discrete indices related to
angular momenta. For $B \ll \Lambda_{\rm QCD}^2$ ($\Lambda_{\rm QCD} \sim 200$
MeV: the QCD scale), the analyses proceed as in usual quark models, while
special cares are needed for strong fields, $B \sim \Lambda_{\rm QCD}^2$,
especially when we treat short range correlations such as the Fermi-Breit-Pauli
interactions. We compute the energy spectra of mesons up to energies of $\sim
2.5$ GeV and construct the meson resonance gas. Within the assumption that the
constituent quark masses are insensitive to magnetic fields, the phase space
enhancement for mesons significantly increases the entropy, assisting a
transition from a hadron gas to a quark gluon plasma.
