Three-dimensional Analytical Description of Magnetised Winds from
  Oblique Pulsars
  Rotating neutron stars, or pulsars, are plausibly the source of power behind
many astrophysical systems, such as gamma-ray bursts, supernovae, pulsar wind
nebulae and supernova remnants. In the past several years, 3D numerical
simulations made it possible to compute pulsar spindown luminosity from first
principles and revealed that oblique pulsar winds are more powerful than
aligned ones. However, what causes this enhanced power output of oblique
pulsars is not understood. In this work, using time-dependent 3D
magnetohydrodynamic (MHD) and force-free simulations, we show that, contrary to
the standard paradigm, the open magnetic flux, which carries the energy away
from the pulsar, is laterally non-uniform. We argue that this non-uniformity is
the primary reason for the increased luminosity of oblique pulsars. To
demonstrate this, we construct simple analytic descriptions of aligned and
orthogonal pulsar winds and combine them to obtain an accurate 3D description
of the pulsar wind for any obliquity. Our approach describes both the warped
magnetospheric current sheet and the smooth variation of pulsar wind properties
outside of it. We find that generically the magnetospheric current sheet
separates plasmas that move at mildly relativistic velocities relative to each
other. This suggests that the magnetospheric reconnection is a type of driven,
rather than free, reconnection. The jump in magnetic field components across
the current sheet decreases with increasing obliquity, which could be a
mechanism that reduces dissipation in near-orthogonal pulsars. Our analytical
description of the pulsar wind can be used for constructing models of pulsar
gamma-ray emission, pulsar wind nebulae, and magnetar-powered core-collapse
gamma-ray bursts and supernovae.
