  Heavy ion collisions, produced in particle accelerators, lead to the
formation of a new state of matter, known as the quark gluon plasma. It is not
possible to observe directly the plasma, where quarks and gluons are not
confined into hadrons. All the available information comes from the particles
that reach the detectors after the strongly interacting matter hadronizes.
Among those particles, one that plays an important role is the charmonium
J/$\psi$ heavy meson, made of a $ c \bar c$ quark anti-quark pair. The fraction
of such particles produced in a heavy ion collision is related to the
dissociation level caused by the plasma. On the other hand, the dissociation of
$J/\Psi $ in the plasma is influenced by the temperature and the density of the
medium and also by the presence of magnetic fields, that are produced in non
central collisions. A very interesting tool to study stability of physical
systems is the configuration entropy (CE). In recent years many examples in
various kinds of physical systems appeared in the literature, where an increase
in the CE is associated with an increase in the instability of the system. In
this article we calculate the CE for charmonium quasistates inside a plasma
with a magnetic field background, in order to investigate how the instability,
corresponding in this case to the dissociation in the thermal medium, is
translated into the dependence of the CE on the field.
