Microchannel plate response to solar energetic particles and consequences for solar-wind measurements on ESA's Vigil mission

Abstract

Space weather forecasting aims at predicting the impacts of the Sun, interplanetary space, and the planetary environment on biological and technological systems. To monitor space weather, the European Space Agency is developing the Vigil mission. Vigil will carry the Plasma Analyser (PLA) instrument. We investigate the expected impact of Solar Energetic Particles (SEPs) on PLA. We analyse previous measurements from Solar Orbiter's Solar Wind Analyser (SWA) Electron Analyser System (EAS) that, like PLA, uses a microchannel plate (MCP) as its detector. Using a fitting algorithm, we extract the number of erroneous counts created by the interaction between SEPs and the MCP. Using SEP flux measurements from Solar Orbiter's Energetic Particle Detector (EPD) and multilinear regression, we establish a linear relationship between the number of erroneous counts and SEP fluxes. We define an SEP index, characterizing the impact of SEP events on EAS measurements. We then simulate PLA measurements during SEP events characterized by their SEP index. We show that moderate SEP events cause significant discrepancies in PLA plasma moment estimations under common solar-wind conditions. Based on our results, we propose a correction method for erroneous counts created by SEPs in instruments such as EAS and PLA.