Magnetic dynamos in white dwarfs -- I. Explaining the dearth of bright
  intermediate polars in globular clusters
  Recently, Bahramian et al. investigated a large sample of globular clusters
(GCs) and found that bright intermediate polars (IPs) are a factor of 10 less
frequent in GCs than in the Galactic field. We theoretically investigate here
this discrepancy based on GC numerical simulations. We found that, due to
disruptive dynamical interaction, there is on average a reduction of only half
of bright IP progenitors, which is clearly not enough to explain the observed
deficiency. However, if the rotation- and crystallization-driven dynamo
scenario recently proposed by Schreiber et al. is incorporated in the
simulations, the observed rareness of bright IPs in GCs can be reproduced. This
is because bright cataclysmic variables in GCs are typically very old systems
($\gtrsim$ 10 Gyr), with white dwarfs that almost fully crystallized before
mass transfer started, which does not allow strong magnetic fields to be
generated. The observed mass density of bright IPs in GCs can be recovered if
around one third of the bright cataclysmic variables dynamically formed through
mergers have magnetic field strengths similar to those of IPs. We conclude that
the observed paucity of bright IPs in GCs is a natural consequence of the newly
proposed rotation- and crystallization-driven dynamo scenario.
