  In this paper we consider a simple two-fluid model for pulsar glitches. We
derive the basic equations that govern the spin evolution of the system from
two-fluid hydrodynamics, accounting for the vortex mediated mutual friction
force that determines the glitch rise. This leads to a simple "bulk" model that
can be used to describe the main properties of a glitch event resulting from
vortex unpinning. In order to model the long term relaxation following the
glitch our model would require additional assumptions regarding the repinning
of vortices, an issue that we only touch upon briefly. Instead, we focus on
comparing the phenomenological model to results obtained from time-evolutions
of the linearised two-fluid equations, i.e. a "hydrodynamic" model for
glitches. This allows us to study, for the first time, dynamics that was
"averaged" in the bulk model, i.e. consider the various neutron star
oscillation modes that are excited during a glitch. The hydro-results are of
some relevance for efforts to detect gravitational waves from glitching
pulsars, although the conclusions drawn from our rather simple model are
pessimistic as far as the detectability of these events is concerned.
