Classification of Magnetohydrodynamic Simulations using Wavelet Scattering Transforms

TL;DR

This paper demonstrates that Wavelet Scattering Transforms combined with linear discriminant analysis effectively classify magnetohydrodynamic turbulence simulations and density fields in the interstellar medium, outperforming other non-Gaussian analysis methods.

Contribution

The study introduces a novel application of WST-LDA for classifying MHD turbulence and density fields, showing robustness and high accuracy in complex astrophysical data.

Findings

WST-LDA classifies MHD simulations with up to 97% accuracy.

WST-LDA is robust to observational artifacts like striping and missing data.

The method can extract magnetic field direction in sub-Alfvénic turbulence.

Abstract

The complex interplay of magnetohydrodynamics, gravity, and supersonic turbulence in the interstellar medium (ISM) introduces non-Gaussian structure that can complicate comparison between theory and observation. We show that the Wavelet Scattering Transform (WST), in combination with linear discriminant analysis (LDA), is sensitive to non-Gaussian structure in 2D ISM dust maps. WST-LDA classifies magnetohydrodynamic (MHD) turbulence simulations with up to a 97\% true positive rate in our testbed of 8 simulations with varying sonic and Alfv\'{e}nic Mach numbers. We present a side-by-side comparison with two other methods for non-Gaussian characterization, the Reduced Wavelet Scattering Transform (RWST) and the 3-Point Correlation Function (3PCF). We also demonstrate the 3D-WST-LDA and apply it to classification of density fields in position-position-velocity (PPV) space, where density correlations can be studied using velocity coherence as a proxy. WST-LDA is robust to common observational artifacts, such as striping and missing data, while also sensitive enough to extract the net magnetic field direction for sub-Alfv\'{e}nic turbulent density fields. We include a brief analysis of the effect of point spread functions and image pixelization on 2D-WST-LDA applied to density fields, which informs the future goal of applying WST-LDA to 2D or 3D all-sky dust maps to extract hydrodynamic parameters of interest.