  We study the partial decay widths of the charmonium states ($J/\psi$,
$\psi(3686)$, $\psi(3770)$, $\chi_{c0}$, $\chi_{c2}$) to $D\bar D$ ($D^+D^-$ or
$D^0\bar {D^0}$) in isospin asymmetric nuclear matter, in the presence of
strong magnetic fields. The in-medium partial decay widths of charmonium states
to $D\bar D$ are calculated within a light quark--antiquark pair creation
model, namely the $^3P_0$ model, using the in--medium masses of the charmonia
as well as $D$ and $\bar D$ mesons in the magnetized nuclear matter obtained
within a chiral effective model. The presence of a magnetic field leads to
Landau quantization of the energy levels of the proton in the nuclear medium.
The effects of magnetic field and isospin asymmetry on the charmonium decay
widths to $D\bar D$ are found to be quite prominent. The effects of the
anomalous magnetic moments have also been taken into consideration for
obtaining the in-medium masses of these heavy flavour mesons, used to calculate
the partial decay widths of the charmonium states. The medium modifications of
the charmonium decay widths can have observable consequences on the production
of the charmed mesons in high energy asymmetric heavy ion collision
experiments.
