  A pictorial explanation for shear-Hall instability is suggested and shows
that the shear flow is not necessary for the instability because its role can
be played by the Hall effect of an inhomogeneous background magnetic field.
Linear stability analysis for a simple model of magnetic field varying
periodically in space confirms such a 'double Hall' instability. Numerical
computations show a considerable increase in Ohmic dissipation rate at the
nonlinear stage of instability development. Field dissipation has a spiky
character associated with magnetic reconnection in current sheets and X-points.
Double Hall instability can be significant for magnetic field dissipation in
neutron star crusts and, possibly, in the solar corona.

Plasma Physics;Solar and Stellar Astrophysics;Fluid Dynamics