  Gravitational effect of "magnetic type" -- those having a curl-like character
over large spheres -- are investigated, for isolated systems. The
Bondi-Sachs-Newman-Penrose formalism clarifies a number of points, especially
related to radiation memory. It is shown that the "memory tensor" is equivalent
to the change in Bondi shear, from before to after the emission of radiation.
This means that if magnetic radiation memory is present, at least one of the
intervals bracketing the radiation must have non-zero magnetic shear but
vanishing radiation. Such intervals, called here CPMS regimes, are shown to be
necessarily non-stationary, however, raising a variety of technical and
interpretative issues. In linearized general relativity, the gravitational
fields due to point magnetic quadrupoles with arbitrary time-dependence are
computed, and some of their physics studied. In the far zone, there is a
red-shift effect which could be searched for astrophysically: light coming from
behind a source generating magnetic shear would be red-shifted by an amount
varying with the angle around the source of shear, and in the far-field limit
this red-shift goes inversely with the impact parameter. Induction-zone effects
are also considered. An induction-zone memory effect should exist which could
possibly be within the reach of laboratory experiments, but no good candidates
for astrophysically detectable effects are found. Also a quadrupole will induce
test particles to move in such a fashion as to create an opposing quadrupole,
an effect reminiscent of Lenz's law.
