Jovian electrons in the inner heliosphere

Proposing a new source spectrum based on 30 years of measurements

¹ Institut für Experimentelle und Angewandte Physik, Christian-Albrechts Universität zu Kiel, Leibnizstraße 11, 24118 Kiel, Germany
e-mail: vogt@physik.uni-kiel.de
² Université Libre de Bruxelles, Service de Physique Statistique et des Plasmas, CP 231, 1050 Brussels, Belgium
³ Centre for Space Research, North-West University, 2520 Potchefstroom, South Africa

Received: 8 August 2017
Accepted: 20 December 2017

Abstract

Context. Since the Pioneer 10 flyby of Jupiter it has become well known that electrons of Jovian origin dominate the lower MeV range of charged energetic particles in the inner heliosphere.

Aims. Because the Jovian source can be treated as point-like in numerical models, many attempts to investigate charged particle transport in the inner heliosphere have utilized Jovian electrons as test particles. The reliability of the derived parameters for convective and diffusive transport processes are therefore highly dependent on an accurate estimation of the Jovian source spectrum. In this study we aim to provide such an estimation.

Methods. In this study we have proposed a new electron source spectrum, specified at the boundary of the Jovian magnetosphere, fitted to flyby measurements by Pioneer 10 and Ulysses, with a spectral shape also in agreement with measurements at Earth’s orbit by Ulysses, Voyager 1, ISEE and SOHO.

Results. The proposed spectrum is consistent with all previous theoretical suggestions, but deviates considerably in the lower MeV range which was inaccessible to those studies.