The MHD continuum with a radial electric field

Abstract

The effects of a radial electric field, which is ubiquitous in stellarators, are considered when a system of reduced-MHD equations is derived from a gyro-kinetic Vlasov–Maxwell system. The resulting equations for the MHD continuum have been implemented into the continuum code CONTI. For a tokamak case, the MHD continuum is calculated and compared with a gyro-kinetic continuum calculated using the EUTERPE code, where good agreement of the obtained continua could be shown. Finally, MHD continua including the radial electric field are calculated for Wendelstein 7-X. Interestingly, for these examples, most of the gaps in the continuous spectrum of Alfvén waves below 200 kHz disappear.