Marfes from radiative condensation instability of electrostatic drift waves in tokamak edge plasmas

Abstract

It is shown that non-equilibrium radiative cooling can give rise to a condensational instability of the drift waves in an inhomogeneous magnetized plasma. The corresponding particle and heat transport coefficients are estimated by means of the conventional quasi-linear theory. The appearance of electrostatic edge turbulence and marfes on the inboard edge of tokamak plasmas may be attributed to such a radiation driven drift wave instability.

Sustained edge-localized-modes suppression and radiative divertor with an impurity-driven instability in tokamak plasmas

“…Due to the strong stabilizing effect from parallel conductivities, the instability coupled to ion acoustic wave only occurs in very narrow T e range and is usually with low frequency (<kHz) [20][21][22]. In inhomogeneous magnetized plasmas, the radiation condensation instability can also couple to drift wave and cause the cross-field particle and energy transport [23][24][25][26]. Drift wave, universally presents in tokamak edge, needs a dissipation mechanism to induce cross-field transport through a phase shift between the density and potential variation.…”

“…Coronal equilibrium is assumed to calculate L z for simplicity, and the impact of noncoronal effects [39] and the relevance of this near the X-point is not yet known and outside of the scope of this work. In tokamaks with strong magnetic field [23,25], the instability can couple to drift waves due to E × B convection across the magnetic field lines, which originates from the time…”

Radiative Alfvén condensation instability

“…Such investigations for collision-dominated plasmas of relevance to the tokamak edge have been carried out in literature. [10][11][12] The extensively used electrostatic approximation is, however, valid only for low ␤ plasmas, where ␤ϭ8nT e /B 2 Ͻ(m e /m i ). At higher values of ␤, the coupling of radiative effects to magnetic perturbations in the plasma such as the shear and compressional Alfvén waves, can also be significant.…”

Radiative Magnetoacoustic Condensation Instability in High-Beta Plasmas

“…We note that for finite obliqueness ðk x 6 ¼ 0Þ this mode reduces to the compressional Alfve´n mode which causes compression of both the plasma density and magnetic field lines. When we consider the perpendicular propagation ðk z ¼ 0Þ the mode represented by (7) and slow magnetosonic mode defined by (8) disappear, but (8) provides only the dispersion relation for the fast magnetosonic waves in which the sum of the magnetic and thermal pressures gives rise to the restoring force and the plasma mass density ðn e0 m e þ n i0 m i Þ provides the inertia. Our interest here is to examine the combined effects of the electron inertia ðl e Þ and electron and ion temperature fluctuations on the fast magnetosonic waves propagating perpendicular to the external magnetic field (k z ¼ 0 and k x ¼ k).…”