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On the validity of the guiding-center approximation in the presence of strong magnetic gradients (1703.05239v2)
Published 15 Mar 2017 in physics.plasm-ph
Abstract: The motion of a charged particle in a nonuniform straight magnetic field with a uniform magnetic-field gradient is solved exactly in terms of elliptic functions. The connection between this problem and the guiding-center approximation is discussed. It is shown that, for this problem, the predictions of guiding-center theory agree very well with the orbit-averaged particle motion and hold well beyond the standard guiding-center limit $\epsilon \equiv \rho/L \ll 1$, where $\rho$ is the gyromotion length scale and $L$ is the magnetic-field gradient length scale.