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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 center

A particle with pitch angle 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.

straight and narrow

On the other hand, a particle with pitch angle is free to move anywhere and readily travels out of the magnetic mirror.

trapped in the mirror

In a magnetic mirror geometry, particles with pitch angles in the following range are trapped within the magnetic mirror:

into the loss cone

However, particles with are said to be in the loss cone and can escape the magnetic mirror.

Last modified May 16, 2005 by Randy Russell.

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