Classical Electrodynamics · Problem 12.10

Radiating Systems, Multipole Fields and Radiation — John David Jackson

Physics — E&M · trapped-particles-earths-magnetic-field

Problem

A charged particle finds itself instantaneously in the equatorial plane of the earth's magnetic field (assumed to be a dipole field) at a distance RR from the center of the earth. Its velocity vector at that instant makes an angle α\alpha with the equatorial plane (v∥/v⊥=tan⁡αv_\parallel/v_\perp = \tan\alpha). Assuming that the particle spirals along the lines of force with a gyration radius a≪Ra \ll R, and that the flux linked by the orbit is a constant of the motion, find an equation for the maximum magnetic latitude λ\lambda reached by the particle as a function of the angle α\alpha. Plot a graph (not a sketch) of λ\lambda versus α\alpha. Mark parametrically along the curve the values of α\alpha for which a particle at radius RR in the equatorial plane will hit the earth (radius R0R_0) for R/R0=1.2,1.5,2.0,2.5,3,4,5R/R_0 = 1.2, 1.5, 2.0, 2.5, 3, 4, 5.

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