  We study collective oscillations of Majorana neutrinos in some of the most
extreme astrophysical sites such as neutron star merger remnants and
magneto-rotational core-collapse supernovae which include dense neutrino media
in the presence of strong magnetic fields. We show that neutrinos can reach
flavor equilibrium if neutrino transition magnetic moment $\mu_\nu$ is strong
enough, namely when $\mu_\nu/\mu_{\rm{B}} \gtrsim 10^{-14}-10^{-15}$ with
$\mu_{\rm{B}}$ being the Bohr magneton. This sort of flavor equilibrium, which
is not necessarily flavor equipartition, can occur on (short) scales determined
by the strength of the magnetic term. Our findings can have interesting
implications for the physics of such violent astrophysical environments.
