Turbulent transport regimes in the presence of an X-point magnetic configuration

TL;DR

This study investigates how X-point magnetic configurations influence turbulent transport in tokamak edges, revealing that large eddies increase transport while X-points reduce mean free paths but cause more extreme particle displacements.

Contribution

It provides new insights into the effects of X-point magnetic fields on turbulence-driven transport in tokamaks, combining statistical analysis with physical property considerations.

Findings

Large scale eddies enhance transport coefficients.

X-point magnetic fields decrease mean free paths.

X-points increase the population of outliers in particle displacement.

Abstract

We analyze the transport properties of the two-dimensional electrostatic turbulence characterizing the edge of a Tokamak device from the study of test particles motion (passive fluid tracers) following the EXB drift. We perform statistical tests on the tracer population in order to assess both the magnitude and the main features of transport. The role of other physical properties, such as viscosity and inverse energy cascade in the spectrum, is also considered. We outline that large scale eddies are responsible for greater transport coefficients, while the presence of an X-point magnetic field reduces the mean free path of the particles, however generating a larger outliers population with respect to a Gaussian profile.