Propagation of the surface cyclotron O-modes at harmonics of ion and electron cyclotron frequencies

Abstract

Theoretical studies of ordinarily polarized surface waves at the first and second harmonics of the ion and electron cyclotron frequencies propagating across an external steady magnetic field are carried out in the case of a weak plasma spatial dispersion along the normal direction towards the plasma interface when the penetration depths of these waves are much greater than the Larmor radii of plasma particles. These waves are eigenmodes of the planar plasma-dielectric layer-metal waveguide structure which is placed into a steady magnetic field oriented parallel to the plasma surface. Their eigenfrequencies can be either greater than or less than the corresponding harmonics of the ion or electron cyclotron frequencies under different conditions in the waveguide considered. The dependence of their damping rates caused both by collisions between plasma particles and the resonant plasma-wave interaction on the waveguide structure parameters is also studied. A comparison of the collisional damping with the collisionless damping is carried out for these modes. To illustrate the possibility of plasma periphery heating by these modes, the flow of their wave power and the quantity of the absorbed wave power are calculated.

MHD internal transport barrier triggering in low positive magnetic shear scenarios in JET

“…This drive appears to reduce the additional heating power required to trigger an ITB (power threshold) compared with the 'natural' condition without any trigger. Other types of MHD trigger have also been observed with fishbone-like characteristics in ASDEX Upgrade, for example [30]. MHD triggers are not necessarily the only means with which to trigger an ITB, and recent experiments suggest that laser ablation or shallow pellets may also fulfil a similar role.…”

Dispersion relation of azimuthal electromagnetic surface waves on a magnetized plasma column in a dielectric lined slow-wave waveguide

“…The parameters of such discharges depend on many factors, such as type of electromagnetic surface waves used [3]. In this case, the study of surface waves and their excitation by an electron beam on the cylindrical surfaces of a magnetized plasma column has become important [12][13][14][15][16][17]. It is well-known that surface waves are qualitatively a type of electromagnetic oscillations of a bounded medium that on the plasma-vacuum interface are often E-type with field components E z , E x , B y if the interface of two media is the yz plane [18,19].…”

“…Therefore, in the axial magnetized plasma-waveguide the propagation of surface waves along the symmetry axis can produce a long plasma layer. On the other hand, for producing the full column of a plasma (not a plasma layer) by surface waves, a flux of energy towards the symmetry axis of the neutral gas column is necessary that can be produced by an azimuthal electromagnetic surface wave (ASW) [14][15][16][17]. The waves propagate along the azimuthal angle, across an external axial steady magnetic field, referred to as the azimuthal surface wave (ASW).…”

Parametric excitation of surface electron cyclotron X- and O- modes by alternating electric fields

“…Surface electron cyclotron O-modes (SECOM) were found theoretically [3] to propagate along plane plasmadielectric interface, when an external constant magnetic field is parallel to the plasma boundary and penetration depth of the modes is approximately equal to their wavelength. SECOM frequencies decrease if their wave number grows, their damping is determined by both collision (interaction between plasma particles) and kinetic (interaction between particles and plasma interface) mechanisms.…”