Abstract:
The component of the ambipolar field along the magnetic field B, though
weak, may, acting together with the gravitational field, give rise to along-B
"ambipolar wells" where light ions (test particles) in the ionosphere in equatorial
regions are trapped. We also take into account magnetic field wells, especially
in cases when the along- and transverse-B velocities of test particles obey
.
For heavy ions, or, for light ions high up, when the ambipolar trap ceases to
function, the along-B ambipolar- and gravitational field effects may combine
with the magnetic field trap to form a double well for the along-B movement
of test particles. The magnetic field trap and its contribution to the double
well may be nearly stationary for particles obeying
even when collisional effects between the test particles and the background
plasma are incorporated. Ions trapped in wells like this, may "feel" a varying
background, for instance because of Earth rotation, that may be incorporated
as time-variation of parameters in the along-B motion. An along-B kinetic equation
for groups of test particles is solved both for the case of simple wells and
for double wells, including time-varying collisional coefficients and additional
fields, and in some cases analytic solutions are obtained. Peculiar along-B
distribution functions may arise due to the time-dependency of coefficients
and to various combinations of collision- and field parameter values. In particular
"breathing" distributions that alternate between wide and narrow forms in phase-space
may arise, and also distributions where strange attractors may play some role.