A local interstellar spectrum for galactic electrons

TL;DR

This paper derives a detailed local interstellar spectrum for galactic electrons from 1 MeV to 50 GeV, using Voyager 1 and PAMELA data, highlighting a spectral break between 800 MeV and 2 GeV.

Contribution

It provides a comprehensive, energy-dependent LIS model for galactic electrons, incorporating a spectral break and improved understanding of low-energy electron spectra.

Findings

LIS exhibits a power law of E^(-1.55) below 1 GeV.

Above 5 GeV, LIS follows a power law of E^(-3.15).

A spectral break occurs between 800 MeV and 2 GeV.

Abstract

A heliopause spectrum at 122 AU from the Sun is presented for galactic electrons over an energy range from 1 MeV to 50 GeV that can be considered the lowest possible local interstellar spectrum (LIS). The focus is on the spectral shape of the LIS below 1.0 GeV. The study is done by using a comprehensive numerical model for solar modulation in comparison with Voyager 1 observations at 110 AU from the Sun and PAMELA data at Earth. Below 1.0 GeV, this LIS exhibits a power law,E to the power -(1.55+-0.05), where E is the kinetic energy. However, reproducing the PAMELA electron spectrum averaged for 2009, requires a LIS with a different power law of the form E to the power -(3.15+-0.05) above about 5 GeV. Combining the two power laws with a smooth transition from low to high energies yields a LIS over the full energy range that is relevant and applicable to the modulation of cosmic ray electrons in the heliosphere. The break occurs between 800 MeV and 2 GeV as a characteristic feature of this LIS.