CR Driven Multi-phase Gas Formed via Thermal Instability
  Cosmic rays (CRs) are an important energy source in the circum-galactic
medium (CGM) that impact the multi-phase gas structure and dynamics. We perform
two-dimensional CR-magnetohydrodynamic simulations to investigate the role of
CRs in accelerating multi-phase gas formed via thermal instability. We compare
outflows driven by CRs to those driven by a hot wind with equivalent momentum.
We find that CRs driven outflow produces lower density contrast between cold
and hot gas due to non-thermal pressure support, and yields a more filamentary
cloud morphology. While entrainment in a hot wind can lead to cold gas
increasing due to efficient cooling, CRs tend to suppress cold gas growth. The
mechanism of this suppression depends on magnetic field strength, with CRs
either reducing cooling or shredding the clouds by differential acceleration.
Despite the suppression of cold gas growth, CRs are able to launch the cold
clouds to observed velocities without rapid destruction. The dynamical
interaction between CRs ad multi-phase gas is also sensitive to the magnetic
field strength. In relatively strong fields, the CRs are more important for
direct momentum input to cold gas. In relatively weak fields, the CRs impact
gas primarily by heating, which modifies gas pressure.
