Turbulent dynamo in the two-phase interstellar medium
  Magnetic fields are a dynamically important component of the turbulent
interstellar medium (ISM) of star-forming galaxies. These magnetic fields are
due to a dynamo action, which is a process of converting turbulent kinetic
energy to magnetic energy. A dynamo that acts at scales less than the turbulent
driving scale is known as the turbulent dynamo. The ISM is a multiphase medium
and observations suggests that the properties of magnetic fields differ with
the phase. Here, we aim to study how the properties of the turbulent dynamo
depend on the phase. We simulate the non-isothermal turbulent dynamo in a
two-phase medium (most previous work assumes an isothermal gas). We find that
the growth rate of magnetic fields in the exponentially growing stage is
similar in both the phases, and this is because of a roughly equal amount of
vorticity being generated in each phase. We further compute each term
responsible for amplification and destruction of vorticity and show that the
amplification of vorticity by turbulent motions is a dominant term (similar in
both the phases) followed by the baroclinic term (only present in
non-isothermal gases, higher in the warm phase) and the term for viscous
interactions in the presence of logarithmic density gradients (higher in the
cold phase). We find that the final ratio of magnetic to turbulent kinetic
energy is lower due to a stronger Lorentz force. We find that the
non-isothermal turbulent dynamo is less efficient than its isothermal
counterpart.
