Stabilizing effect of magnetic helicity on magnetic cavities in the intergalactic medium

Observations have shown that above some galactic disks there exist hot
under-dense bubbles in the intergalactic medium. Due to their low
density, they rise and seem to survive for tens of millions of years.
However, the Kelvin-Helmholtz instability should lead to a break up
at a much shorter time scale.
We test if an internal magnetic field with helicity can stabilize the
bubbles. This is motivated by the realizability condition that imposes a
lower bound for the magnetic energy in presence of magnetic helicity. We
compare the non-magnetic case with two cases with a internal helical
magnetic field. Both magnetic fields have the same energy, but different
helicities by a factor of 4. We run numerical simulations that clearly
show that a highly helical magnetic field can stabilize the bubbles for
several of tens of millions of years. The energy required is much lower
than for a stabilizing external magnetic field.