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We investigate the motions of charged particles in the near horizon region ofan extreme Kerr black hole with weak electromagnetic fields. There is anenhanced symmetry in the NHEK geometry. We find that when the electromagneticfield respects this enhanced symmetry, which we refer to as the maximallysymmetric electromagnetic (MSEM) field, the equations of motion of chargedparticles get simplified into a set of decoupled first-order differentialequations. We discuss the motions of charged particles in two MSEM fields, onebeing the force-free field and the other being the vacuum fields. Even thoughthe radial motions are similar to the geodesics in NHEK geometry, the angularmotions could be affected by the electromagnetic field significantly. Inparticular, for the vacuum solution which is produced by a weakly charged blackhole, there exist stable vortical motions if the electromagnetic parameter isabove the critical value $\mB_c = \sqrt{3}$. These vortical motions do notcross the equatorial planes, and the charged particles in them radiatenon-thermally. We discuss the corresponding astrophysical implications.

Electromagnetic effects on charged particles in NHEK