Reconnection from a Turbulence Perspective

TL;DR

This paper investigates the spectral properties of laminar magnetic reconnection using kinetic simulations, revealing a three-phase process with energy cascade characteristics similar to turbulence.

Contribution

It demonstrates that laminar reconnection exhibits a Kolmogorov-like energy cascade and analyzes the spectral evolution and anisotropy during reconnection.

Findings

Energy spectrum shows a double power-law behavior during steady reconnection.

Reconnection rate correlates with the energy spectrum near the ion inertial length.

Reconnection reduces spectral anisotropy, approaching isotropy by the end.

Abstract

The spectral properties associated with laminar, anti-parallel reconnection are examined using a 2.5D kinetic particle in cell (PIC) simulation. Both the reconnection rate and the energy spectrum exhibit three distinct phases: an initiation phase where the reconnection rate grows, a quasi-steady phase, and a declining phase where both the reconnection rate and the energy spectrum decrease. During the steady phase, the energy spectrum exhibits approximately a double power-law behavior, with a slope near -5/3 at wavenumbers smaller than the inverse ion inertial length, and a slope steeper than -8/3 for larger wavenumbers up to the inverse electron inertial length. This behavior is consistent with a Kolmogorov energy cascade and implies that laminar reconnection may fundamentally be an energy cascade process. Consistent with this idea is that the reconnection rate exhibits a rough correlation with the energy spectrum at wave numbers near the inverse ion inertial length. The 2D spectrum is strongly anisotropic with most energy associated with the wave vector direction normal to the current sheet. Reconnection acts to isotropize the energy spectrum, reducing the Shebalin angle from an initial value of 70 degrees to about 48 degrees (nearly isotropic) by the end of the simulation.