  Attention is drawn to a fundamental difference between the physical
mechanisms responsible for the magnetic field freezing-in effect in spatially
isotropic (collisional) and strongly anisotropic (collisionless) plasmas. (The
first case is characteristic of internal regions of the Sun and other stars;
the second, for the solar corona, interplanetary and interstellar medium,
planetary ionospheres and magnetospheres, cometary tails.) It is shown that
particles of a collisionless plasma remain in the same field line during their
motion because of the properties of electrodynamic drift which stem from the
divergence-free character of the magnetic field and the equipotentiality of the
field lines (but not as a result of the appearance of induction currents,
compensating variations of the external magnetic flux through a closed contour,
as in the case of isotropic conductivity of the plasma).
