  A new gauge-free electromagnetic gyrokinetic theory is developed, in which
the gyrocenter equations of motion and the gyrocenter phase-space
transformation are expressed in terms of the perturbed electromagnetic fields,
instead of the usual perturbed potentials. Gyrocenter polarization and
magnetization are derived explicitly from the gyrocenter Hamiltonian, up to
first order in the gyrocenter perturbation expansion. Expressions for the
sources in Maxwell's equations are derived in a form that is suitable for
simulation studies, as well as kinetic-gyrokinetic hybrid modeling.
