  In order to address the generation of neutron star magnetic fields, with
particular focus on the dichotomy between magnetars and radio pulsars, we
consider the properties of dynamos as inferred from other astrophysical
systems. With sufficiently low (modified) Rossby number, convective dynamos are
known to produce dipole-dominated fields whose strength scales with convective
flux, and we argue that these expectations should apply to the convective
proto-neutron stars at the centers of core-collapse supernovae. We analyze a
suite of three-dimensional simulations of core collapse, featuring a realistic
equation of state and full neutrino transport, in this context. All our
progenitor models, ranging from 9 solar masses to 25 solar masses, including
one with initial rotation, have sufficiently vigorous proto-neutron-star
convection to generate dipole fields of order ~10^15 gauss, if the modified
Rossby number resides in the critical range. Thus, the magnetar/radio pulsar
dichotomy may arise naturally in part from the distribution of core rotation
rates in massive stars.
