A proton trapped on the shell of the Earth's dipole has gyration period

PHYSICS · Multi-part · Fermi University Physics · Plasma Physics · The plasma state and single-particle motion · Laboratory, industrial and space plasmas

Plasma Physics, Ch Slow changes and what survives them: adiabatic invariants, mirrors and trapped orbits

Problem

A proton trapped on the

L=5

shell of the Earth's dipole has gyration period

0.090\,\mathrm{s}

, bounce period

4.0\,\mathrm{s}

and drift period

7.0\,\mathrm{min}

. A geomagnetic storm compresses the magnetosphere on a timescale of about

2.0\,\mathrm{min}

. ((a)) State, with reasoning based on comparing this timescale with each of the three periods, which of

\mu

J

and

\Phi

survive the compression and which is broken. ((b)) Describe in words what happens to the particle as a result.

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