|Auteur(s) supplémentaire(s)||M. Maksimovic1, F. Pantellini1, L. Lamy1, A. Vecchio1, A. Hilgers2, C.J. Owen3|
|Institution(s) supplémentaire(s)||1LESIA and CNRS, Observatoire de Paris-Meudon, Meudon, France, 2ESA, ESTEC, Noordwijk, The Netherlands, 3MSSL/UCL, Dorking, Surrey, UK.|
This presentation focuses on numerical simulations of the Solar Orbiter spacecraft/plasma interactions performed with the Spacecraft Plasma Interaction System (SPIS) software (http://dev.spis.org/projects/spine/home/spis/). This toolkit aims at modelling spacecraft-plasma interactions, based on an electrostatic 3-D unstructured particle-in-cell plasma model. New powerful SPIS functionalities were recently delivered within the extension of the software: SPIS-Science (ESA contract). This version revolutionizes spacecraft/plasma interactions as users are now able to model and configure plasma instrument such as Langmuir probes or particle detectors taking into account instrument characteristics like geometry, materials, energy ranges and resolution, output frequency, field of view.
The Solar Orbiter spacecraft (M-class ESA Cosmic Vision with NASA participation, to be launched in October 2018), is dedicated to the Sun observation with in-situ and remote sensing instruments, brought as close as 0.28 A.U. from the star. In this hot and dense environment the entire satellite will be submitted to high radiations and temperatures (up to 10 Solar constants). Material responses to environment constraints (heat, U.V. flux, photoemission, secondary electron emission) might bias the scientific instrument measurements.
Among the 10 Solar orbiter Instruments, the Electron Analyzer System (EAS) will collect the thermal electron Velocity Distribution Function (VDFs) and the Radio and Plasma Waves (RPW) will measure the ambient electric field fluctuation from DC to several kHz.
Previous numerical simulations already showed the EAS detector will be affected by important fluxes of low energy secondary and photoelectrons, emitted by Solar Orbiter itself, and deflected by local potential barriers due to covering material charging, ion wake and secondary electron / photoelectron high densities. These phenomena result in a bias of the measured thermal electrons VDFs. Compared with theoretical undisturbed VDFs, EAS measures a high increase of density (of more than 130% at Solar Orbiter perihelion) and a discrepancy in electron flux origin due to particle deflections generated by the satellite itself and its various element potentials. We will review in this presentation the latest results obtained for the modelling of EAS.
As for RPW, the experiment consists in 3 conducting antennas of 6 m length which will charge independently according to local environment conditions. The potential difference between them will allow to recover the ambient electric field in the plasma, knowing the effective length of the stacers. However those 3 antennas will also emit electron clouds in their vicinity (modifying the local electrostatic pattern). They also might bend due to material expansion on their sunlit faces (at the closest distance to the Sun, temperature expected on the antennas will be about 500 – 600° C). Those disturbing issues need to be investigated through simulations.