Gyrosymmetry: Global Considerations

Abstract

In the guiding center theory, smooth unit vectors perpendicular to the magnetic field are required to define the gyrophase. The question of global existence of these vectors is addressed using a general result from the theory of characteristic classes. It is found that there is, in certain cases, an obstruction to global existence. In these cases, the gyrophase cannot be defined globally. The implications of this fact on the basic structure of the guiding center theory are discussed. In particular it is demonstrated that the guiding center asymptotic expansion of the equations of motion can still be performed in a globally consistent manner when a single global convention for measuring gyrophase is unavailable. The latter fact is demonstrated directly by deriving a new expression for the guiding-center Poincaré-Cartan form exhibiting no dependence on the choice of perpendicular unit vectors.

22 pages

References in corpus (1)

• Covariant Lagrangian Methods of Relativistic Plasma Theory

Cited by in corpus (7)

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• On the correspondence between classical geometric phase of gyro-motion and quantum Berry phase
• On the derivation of guiding center dynamics without coordinate dependence