Charged Particle Motion in Earth's Magnetosphere
Magnetic Mirroring and the Loss Cone
A particle's pitch angle increases as it moves into a region of stronger magnetic field and decreases as it moves into a region of weaker field.
In a simple magnetic mirror geometry the magnetic field reaches a minimum value at the center of the geometry and a maximum value at the end. Particles within such a geometry can follow a range of trajectories, as described below.
stuck in the centerA particle with pitch angle |
straight and narrowOn the other hand, a particle with pitch angle |
trapped in the mirrorIn a magnetic mirror geometry, particles with pitch angles in the following range are trapped within the magnetic mirror:
|
into the loss coneHowever, particles with |
cannot
move into a region of stronger magnetic field, so a particle with
(at
the center of the magnetic mirror, where B = Bmin) cannot move away
from the center of the mirror.
is
free to move anywhere and readily travels out of the magnetic mirror.
are
said to be in the loss cone and can escape the magnetic mirror.
