  Disc accretion on to a black hole is often misaligned from its spin axis. If
the disc maintains a significant magnetic field normal to its local plane, we
show that dipole radiation from Lense-Thirring precessing disc annuli can
extract a significant fraction of the accretion energy, sharply peaked towards
small disc radii $R$ (as $R^{-17/2}$ for fields with constant equipartition
ratio). This low-frequency emission is immediately absorbed by surrounding
matter or refracted towards the regions of lowest density. The resultant
mechanical pressure, dipole angular pattern, and much lower matter density
towards the rotational poles create a strong tendency to drive jets along the
black hole spin axis, similar to the spin-axis jets of radio pulsars, also
strong dipole emitters. The coherent primary emission may explain the high
brightness temperatures seen in jets. The intrinsic disc emission is modulated
at Lense-Thirring frequencies near the inner edge, providing a physical
mechanism for low-frequency QPOs.
  Dipole emission requires nonzero hole spin, but uses only disc accretion
energy. No spin energy is extracted, unlike the Blandford-Znajek process.
MHD/GRMHD formulations do not directly give radiation fields, but can be
checked post-process for dipole emission and so self-consistency, given
sufficient resolution. Jets driven by dipole radiation should be more common in
AGN than in X-ray binaries, and in low accretion rate states than high,
agreeing with observation. In non-black-hole accretion, misaligned disc annuli
precess because of the accretor's mass quadrupole moment, similarly producing
jets and QPOs.
