The present talk consists of two parts. The first one is allocated for consideration of the dimension of bilocal meson fields for quark-antiquark meson systems, which have been so far treated as the bosonic fields independent of constituent quark flavors, in the covariant oscillator quark model. Revisiting the electromagnetic currents of quark-antiquark meson systems, we show that the bilocal meson fields should be bosonic for light-quark meson systems, while fermionic for heavy-light and heavy-heavy meson systems.
In the second part we apply the effective electromagnetic interactions of meson systems derived in the first part to radiative decay processes for the excited states of light-quark mesons. The calculated results for the $\pi \gamma$ decay widths of the $a_1(1260)$, $a_2(1320)$, $b_1(1235)$ and $\pi_2(1670)$ mesons are in fair agreement with experiment, except for the $b_1(1235)$ meson. As for the $\rho(770)^0 \gamma$ decay width of the $f_1(1285)$ the present model strongly supports the experimental results in 1995 and 2016, respectively, of VES and CLAS Collaborations, not the average value by the Particle Data Group.