A Very Local Interstellar Spectrum for Galactic Electrons

TL;DR

This paper derives a new local interstellar spectrum for cosmic ray electrons from 1 MeV to 70 GeV, reconciling Voyager 1 data with Earth-based observations and highlighting spectral features not explained by heliospheric effects.

Contribution

It provides a comprehensive interstellar electron spectrum model that aligns Voyager 1 data with Earth observations, revealing spectral features beyond solar modulation effects.

Findings

Power law spectrum below 0.8 GeV with index -1.55

Spectral index of -3.3 between 2 and 20 GeV during 2006

Discrepancy cannot be explained by heliospheric processes

Abstract

We present a new local interstellar spectrum for cosmic ray electrons over an energy range from 1 MeV to 70 GeV. Below (0.8 plus minus 0.2) GeV it has a power law form, E^-(1.55 plus minus 0.05), with E kinetic energy, which is consistent with previous studies. This is derived from comparing Voyager 1 electron data observed during 2010 with a comprehensive modulation model. However, reproducing the PAMELA electron spectrum observed at Earth during late 2006 and to address an unexpected increase in the electron spectrum between about 2 GeV and up to about 20 GeV, a spectral index of -(3.3 plus minus 0.1) instead of the reported -(3.18 plus minus 0.05) was found for this energy range. This feature cannot be caused by solar modulation or any other process inside the heliosphere.