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arXiv · 2601.07109

Guiding-center dynamics in a screw-pinch magnetic field

Alain J. Brizard
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Abstract

The guiding-center dynamics of charged particles moving in a doubly-symmetric screw-pinch magnetic field is investigated. In particular, we verify that Kruskal's adiabatic-invariant series expansion of the radial action integral associated with the reduced full-orbit radial motion matches the perturbation expansion of the magnetic-moment gyroaction up to first order in magnetic-field non-uniformity. Because the radial action integral is an exact invariant of the full-orbit dynamics, the magnetic moment is therefore represented as non-perturbative integral expression, which can be used to test the validity of the guiding-center approximation.

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Alain J. Brizard. 2026-01-12. Guiding-center dynamics in a screw-pinch magnetic field. https://arxiv.org/abs/2601.07109

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