Evolution of magnetic Kubo number of stochastic magnetic fields during the edge pedestal collapse simulation

TL;DR

This study analyzes the evolution of the magnetic Kubo number during edge pedestal collapse in plasma simulations, showing it remains below unity and supports quasilinear diffusion as the main energy loss mechanism.

Contribution

It provides the first detailed analysis of the magnetic Kubo number evolution during pedestal collapse using nonlinear MHD simulations, highlighting its bounded nature and correlation with fluctuation scales.

Findings

Kubo number remains below 1 during collapse

Quasilinear diffusion model explains energy loss

Correlation lengths relate to magnetic stochastic layer width

Abstract

Using a statistical correlation analysis, we compute evolution of the magnetic Kubo number during an edge pedestal collapse in nonlinear reduced magnetohydrodynamic simulations. The Kubo number is found not to exceed the unity in spite of performing the simulation with a highly unstable initial pressure profile to the ideal ballooning mode. During the edge pedestal collapse, the Kubo number is within the values of $0.2$ and $0.6$ suggesting that the quasilinear diffusion model is sufficient to explain the energy loss mechanism during the pedestal collapse. Temporal evolution of poloidal correlation lengths of pressure fluctuations resembles with that of the Chirikov parameter and the Kubo number; while radial correlation lengths of the pressure fluctuations are strongly correlated with the radial width of the magnetic stochastic layer.