On the induced azimuthal electric field in the current drive of an odd-parity rotating magnetic field

The azimuthal electric field E θ ω, which is induced by the axial oscillating magnetic field B z ω of the odd-parity Rotating Magnetic Field (RMF) scheme, is experimentally found to play an important role in driving the toroidal plasma current. In the odd-parity RMF scheme, E θ ω at the middle plane of the field reversed configuration can generate the so-called punctuated betatron-orbital electrons to drive the toroidal current in addition to the current driven by the transverse component of RMF B r ω, whereas B r ω is the only driving mechanism in the even-parity scheme. In this work, E θ ω (or B z ω) and B r ω are each studied to account for different current driving mechanisms. We report that E θ ω accounts for the more efficient current driving in our experiments.