The guiding-centre equations of motion of a classical charged particle
in a
strong magnetic field and a strongly sheared electric field are derived.
They can
be used to analyse the dynamics of particles in electromagnetic fields
whose
spatial profiles are similar to those observed during the H mode in the
DIII-D
tokamak, for instance. The derivation of the equations of motion is performed
up to second order in the drift parameter by applying a Hamiltonian
pseudocanonical transformation that removes the gyrophase induced by the
magnetic field. The main difference with the standard case of a slowly
varying
electric field relates to the variation of the new gyrophase and to the
expression
for the magnetic moment: mv2⊥/2B
must be replaced by
formula here
The latter case is also reconsidered – mainly to reveal the consequences
of the
removal of a hidden divergence for small parallel velocities resulting
from the
usual averaging transformation.