Solar Wind Electron Strahl – Preparations for Measurement with Solar Orbiter’s SWA/EAS Sensor after Lessons from Helios and Cluster.

Abstract:

The nature of the electron strahl population in the solar wind is a key diagnostic of the connectivity of the magnetic field to the solar atmosphere. As such, its measurement is fundamental to the success of the Solar Orbiter mission, with its scientific goals largely focussed around making the link between physical processes observed remotely in the near-Sun environment and the fields and particle populations detected in situ at the spacecraft. The Electron Analyser System (EAS) is part of the Solar Wind Analysers (SWA) suite of sensors which will be flown on the mission. It will make measurements of the 3D velocity distribution of electrons in the energy range of a few eV up to ~5 keV. In this presentation we first briefly review the expected capabilities of EAS. We then describe the strategies being developed to accurately categorize the electron strahl population with the sensor, with particular reference to our ongoing studies of relevant existing datasets from the Helios and Cluster missions.