Charged Particles in Electromagnetic Fields
In space physics the motion of charged particles in electric and magnetic fields can be described by a test particle approach: the particles are guided by the field but their motion does not affect the field. This approach is valid if the energy density of the magnetic field exceeds that of the particles. In the test particle approach the motion can be separated into two parts: the motion of a guiding center of the particle orbit and a gyration around it. The guiding center motion can be interpreted as the effective motion of the particle, averaged over many gyrations. This concept is applied to drifts in static electromagnetic fields. The adiabatic invariants allow simple estimates of the particle motion in temporally and spatially slowly varying fields; they are applied to the motion of particles in the Earth’s radiation belts. This chapter starts with a brief recapitulation of the basics of electromagnetic field theory.
KeywordsElectromagnetic Field Pitch Angle Radiation Belt Homogeneous Magnetic Field Loss Cone
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