  Aims. We analyze a MUSE optical integral field spectrum of the star-forming
edge-on galaxy IC 1553 in order to study its extraplanar diffuse ionized gas
(eDIG) and the processes shaping its disk-halo interface. Methods. We extracted
the optical emission line properties from the integral field spectrum and
generated the commonly used emission line diagnostic diagrams in order to
analyze the ionization conditions and the distribution of the eDIG.
Furthermore, we performed gravitational potential fitting to investigate the
kinematics of a suspected galactic outflow. Results. We find that the eDIG
scale height has a maximum value of approximately 1.0 kpc and decreases roughly
linearly with the radial distance from the galactic center in projection. The
ionization state of the eDIG is not consistent with a pure photoionization
scenario and instead requires a significant contribution from shock ionization.
This, in addition to the gas kinematics, strongly suggests the presence of a
galactic scale outflow, the origin of which lies at least 1.4 kpc away from the
galactic center. The inferred shock velocity in the eDIG of approximately 225
km s-1 is comparable to the escape velocity estimated from our potential
modelling. The asymmetric distribution of currently star-forming clusters
produces a range of different ionization conditions in the eDIG. As a result,
the vertical emission line profiles vary quantitatively and qualitatively along
the major axis of the galaxy. This analysis illustrates that it is crucial in
studies of the eDIG to use observations that take the spatial and kinematical
distributions into account, such as those done with integral field units, to
form an accurate picture of the relevant physical properties.
