a magnetorotational core-collapse supernova. Bluish colors indicate low entropy, red colors high entropy, and green and yellow intermediate entropy. The vertical is the axis of rotation and shown is a region of $\sim$$1600 \times 800\,\mathrm{km}$. The ultra-strong toroidal magnetic field surrounding the the protoneutron star pushes hot plasma out along the rotation axis. The distorted, double-lobe structure is due to an MHD kink instability akin those seen in Tokamak fusion experiments. Used with permission from Mösta *et al.* 2014 [@moesta:14b].[]{data-label="fig:mhd2014"}](f3.png){width="0.9\columnwidth"}

Despite its overall promise, the neutrino mechanism is very inefficient. Only $\lesssim 5\%$ of the outgoing total electron neutrino and antineutrino luminosity is deposited behind the stalled shock at any moment and much of this deposition is lost again as heated gas flows down, leaves the heating region, and settles onto the protoneutron. The neutrino mechanism may (barely) be able to power ordinary core-collapse supernovae, but it cannot deliver hypernova explosion energies or account for gamma-ray bursts.

An alternative mechanism that may be part of the explanation for such extreme events is the *magnetorotational mechanism*, first suggested by Bisnovatyi-Kogan [@bisno:70] and LeBlanc & Wilson [@leblanc:70]. In its modern form, a very rapidly spinning core collapses to a protoneutron star with 