7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Kinetic theory of the non-diffusive convective flows, generated in the tokamakedge plasma by the parametric inhomogeneous ion cyclotron turbulence in thefast wave heating regime
V. S. Mykhaylenko1, V. V. Mykhaylenko1, Hae June Lee2
1
Plsma Research Center, Pusan National University, Busan, South Korea
2
Department of Electrical Engineering, Pusan National University, Busan, South Korea
vsmikhailenko@pusan.ac.kr

It was found in essentially all fast wave (FW) heatingexperiments in tokamaks, that a significant fraction of theFW power does not appear in the plasma core and is lostpresumably in the cold low density scrape-off layer (SOL)
plasma adjacent to the FW antenna. It was observed [1] inthe FW heating experiments in NSTX tokamak that asignificant part of the edge FW power loss occurs due tothe formation of large heat flux, which flows through theSOL to the divertor.
In this report, we present new two-scale approach [2-4]to the theory of the mesoscale convective flows generatedby the radially inhomogeneous ion cyclotron (IC)parametric microturbulence in the pedestal plasma with asheared poloidal flow. This theory involves the theory of
the microscale IC parametric instabilities of theinhomogeneous plasma, driven by the inhomogeneous
FW, and the theory of the mesoscale evolution of theplasma caused by the mesoscale inhomogeneity of the IC
microturbulence. It was derived in [2, 3] that the spatial
inhomogeneity of the parametric IC turbulence and of thedrift turbulence is at the origin of the sheared poloidal andof the radial compressed non-diffusive convective flows
with radial gradients of the flows velocities. The velocityof the radial compressed convective flow is in thedirection opposite to the gradient of the spectral intensityof the microscale turbulence. In the pedestal plasma, thisconvective flow moves outward of pedestal to SOL region.
This theory gives the possible explanation of theunderlying mechanism of the convective flow formationin the FW heating experiment on NSTX [1]. We foundthat this flow is responsible for a significant part of theFW power loss due to the anomalous non-diffusivetransport of the collisionless dense hot plasma from theedge to the cold low density scrape-off layer (SOL)
plasma, which is delivered eventually to the divertor.

It was found, that the dynamical processes in thepedestal and near SOL are heavily determined by thesheared-compressed convective flows formed in thisregion by the inhomogeneous microturbulence and byinterplay of these convective flows with the sheared
poloidal edge flow of a tokamak plasma. The developedhydrodynamic mesoscale theory [3] reveals the radialconvective flow as the dominant factor in the formation of
the steep pedestal density profile with plasma densitygradient exponentially growing with time.
Because of the presence of such flows in the edge of thetokamak plasma, the conventional modal theory of plasma
stability is not valid for the dynamical edge, where any
perturbation in the compressed-sheared flows experiences
the persistent growing with time spatial distortion. The
new nonmodal theory of the stability of the shearedcompressed flows, which accounts for the effects of the
distortions of the perturbations in edge flows isdeveloped[4].
This work was supported by National R&D Program
through the National Research Foundation of Korea(Grants NRF-2022R1A2C1012808 andNRF-2021M3F7A10844191362)
References.
1. R. J. Perkins, J. C. Hosea, G. J. Kramer,et al. Phys. Rev.
Lett. 109, 045001 (2012).
2. V. S. Mikhailenko, V. V. Mikhailenko, Hae June Lee,
Phys. Plasmas 28, 042304 (2021).
3. V. S. Mikhailenko, V. V. Mikhailenko, Hae June Lee,
Phys. Plasmas 29, 072301 (2022).
4. V. S. Mikhailenko, V. V. Mikhailenko, Hae June Lee,
Phys. Plasmas 30, 052302 (2023).
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