  In galactic disks, the Parker instability results when non-thermal pressure
support exceeds a certain threshold. The non-thermal pressures considered in
the Parker instability are cosmic ray pressure and magnetic pressure. This
instability takes a long time to saturate $(>500 \, \mathrm{Myr})$ and assumes
a background with fixed cosmic ray pressure to gas pressure ratio. In reality,
galactic cosmic rays are injected into localized regions $(< 100
\,\mathrm{pc})$ by events like supernovae, increasing the cosmic ray pressure
to gas pressure ratio. In this work, we examine the effect of such cosmic ray
injection on large scales $ (\sim 1\,\mathrm{kpc})$ in cosmic ray
magnetohydrodynamic simulations using the \texttt{Athena++} code. We vary the
background properties, dominant cosmic ray transport mechanism, and injection
characteristics between our simulation runs. We find the injection will disrupt
the interstellar medium on shorter timescales than the Parker instability. If
cosmic ray transport by advection is dominant, cosmic ray injection disrupts
the disk on short time scales $(<100\,\mathrm{Myr})$. If cosmic ray transport
by the streaming instability is dominant, the injection creates a buoyant flux
tube long after the initial injection $(>150\,\mathrm{Myr})$. Finally, when
cosmic ray transport by diffusion dominates, the injected cosmic rays make an
entire flux tube over pressured in a short time $(\sim 10 \, \mathrm{Myr})$.
This over pressure pushes gas off the tube and drives buoyant rise on time
scales similar to the advection dominated case.
