A Heliopause Spectrum for Electrons

TL;DR

This paper derives a detailed heliopause spectrum for galactic electrons from 1 MeV to 50 GeV, combining observations and numerical modeling to characterize the local interstellar spectrum and its energy-dependent features.

Contribution

It presents the first comprehensive heliopause spectrum for galactic electrons over a broad energy range, integrating Voyager 1 and PAMELA data with solar modulation models.

Findings

The spectrum follows a power law with E^(-1.5) below 1 GeV.

Above 5 GeV, the spectrum follows E^(-3.15).

The spectrum has a break between 800 MeV and 2 GeV.

Abstract

We present a heliopause spectrum for galactic electrons over an energy range from 1 MeV to 50 GeV at 122 AU from the Sun. This spectrum can be considered the lowest possible local interstellar spectrum (LIS). This is obtained by using a comprehensive numerical model for solar modulation in comparison with Voyager 1 observations during 2010 and PAMELA data at Earth. Below about 1 GeV, this LIS exhibits a power law with E^(-(1.5 plus minus 0.1), where E is the kinetic energy of these electrons. Reproducing the PAMELA electron spectrum for 2009 requires a LIS with a different power law above about 5 GeV of the form E^(-3.15 plus minus 0.05). The heliopause spectrum thus consists of two power laws with a break between about 800 MeV and about 2 GeV.