A powerful machine learning technique to extract proton core, beam, and α-particle parameters from velocity distribution functions in space plasmas

¹ Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
e-mail: daniel.vech@lasp.colorado.edu
² Smithsonian Astrophysical Observatory, Cambridge, MA 02138 USA
³ Astrophysical and Planetary Sciences Department, University of Colorado, Boulder, CO, USA
⁴ Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85719, USA
⁵ BWX Technologies, Inc., Washington DC 20002, USA
⁶ Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109, USA

Received: 12 April 2021
Accepted: 18 May 2021

Abstract

Context. The analysis of the thermal part of velocity distribution functions (VDFs) is fundamentally important for understanding the kinetic physics that governs the evolution and dynamics of space plasmas. However, calculating the proton core, beam, and α-particle parameters for large data sets of VDFs is a time-consuming and computationally demanding process that always requires supervision by a human expert.

Aims. We developed a machine learning tool that can extract proton core, beam, and α-particle parameters using images (2D grid consisting pixel values) of VDFs.

Methods. A database of synthetic VDFs was generated, which was used to train a convolutional neural network that infers bulk speed, thermal speed, and density for all three particle populations. We generated a separate test data set of synthetic VDFs that we used to compare and quantify the predictive power of the neural network and a fitting algorithm.

Results. The neural network achieves significantly smaller root-mean-square errors to infer proton core, beam, and α-particle parameters than a traditional fitting algorithm.

Conclusions. The developed machine learning tool has the potential to revolutionize the processing of particle measurements since it allows the computation of more accurate particle parameters than previously used fitting procedures.