Fitting the Galactic Electron Spectrum Measured by Voyager at Low Energies and also by CALET/AMS-2 at High Energies Using a Monte Carlo Diffusion Model for Electron Propagation - One Spectrum Fits All

TL;DR

This study models galactic electron spectra across a vast energy range using a Monte Carlo diffusion approach, successfully matching observations from low to high energies and revealing local origins of electrons.

Contribution

It introduces a Monte Carlo diffusion model that accurately fits electron spectra from MeV to TeV energies, unifying observations with minimal assumptions and highlighting local electron sources.

Findings

Model matches Voyager, AMS-2, and CALET data within a few percent.

Electron spectrum index increases from ~2.1 to 2.4 across energies.

No significant individual sources contribute more than 10-20% of the background.

Abstract

In this paper we compare galactic electron spectra measured up to TeV energies by AMS2 and CALET and that measured by Voyager at the lowest energies down to 1 MeV with that calculated using a Monte Carlo diffusion model for electron propagation in the galaxy. The observations and calculations at both ends of the electron spectrum, differing by a factor ~10^6 in energy, can be matched to within a few percent with a minimal set of assumptions. This includes an electron spectrum which has an index increasing from ~2.1 at the lowest energies to 2.4 at ~1 TeV, along with a diffusion coefficient that remains essentially constant below ~1.5 GV above which it becomes P^0.45. The Monte Carlo calculations indicate that the lowest and highest energy electrons originate within a local region near the galactic plane of size, less than L where L is the thickness of the trapping region. The remarkable agreement to within a few percent between the calculations and measurements from 20 GeV up to ~1 TeV also indicates that there are no individual sources greater than 10-20 percent of the Monte Carlo calculated background that are contributing to the observed electron intensity in this energy range.