The crutial role of the rotating magnetic field in the formation of field reversed configuration*

Understanding the penetration process of rotating magnetic field (RMF) driven by odd-parity RMF (RMFo) antenna may fundamentally enable us to comprehend the heating mechanism of RMF driven field-reversed configuration (FRC), and further allow us to achieve long time (>a few hundreds of milliseconds) FRC maintenance. Choosing parameters related to the PFRC-2 experiment, with wall radius of 5 cm, axial static magnetic field of 300 G, magnetic field induced by the RMF antenna of 12 G, RMF frequency of 4 MHz, RMF antenna current of 1000 A, plasma density of 10¹³ cm^-3, and electron temperature of 200 eV, full multiphysics particle-field interaction simulations imply that the FRC is formed after 10 RMF periods, and the azimuthal electric field is responsible for accelerating electrons and gradually penetrating the core plasma region; on the other hand, when a higher RMF magnetic field ( 30 G) is applied, the azimuthal plasma current induced by RMF becomes penetrating in a non-azimuthally symmetrical form, as if the azimuthal plasma current drives spiral field penetration.