Deriving the bulk properties of solar wind electrons observed by Solar Orbiter. A preliminary study of electron plasma thermodynamics

Nicolaou, G., Wicks, Robert, Owen, C. J., Kataria, D. O. and al, et (2021) Deriving the bulk properties of solar wind electrons observed by Solar Orbiter. A preliminary study of electron plasma thermodynamics. Astronomy & Astrophysics, 656. A10. ISSN 0004-6361

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Context. We demonstrate the calculation of solar wind electron bulk parameters from recent observations by Solar Wind Analyser Electron Analyser System on board Solar Orbiter. We use our methods to derive the electron bulk parameters in a time interval of a few hours. We attempt a preliminary examination of the polytropic behavior of the electrons by analyzing the derived electron density and temperature. Moreover, we discuss the challenges in analyzing the observations due to the spacecraft charging and photo-electron contamination in the energy range < 10 eV.
Aims. We derive bulk parameters of thermal solar wind electrons by analyzing Solar Orbiter observations and we investigate if there is any typical polytropic model that applies to the electron density and temperature fluctuations.
Methods. We use the appropriate transformations to convert the observations to velocity distribution functions in the instrument frame. We then derive the electron bulk parameters by a) calculating the statistical moments of the constructed velocity distribution functions and b) by fitting the constructed distributions with analytical expressions. We firstly test our methods by applying them to an artificial data-set, which we produce by using the forward modeling technique.
Results. The forward model validates the analysis techniques which we use to derive the electron bulk parameters. The calculation of the statistical moments and the fitting method determines bulk parameters that are identical within uncertainty to the input parameters we use to simulate the plasma electrons in the first place. An application of our analysis technique to the data reveals a nearly isothermal electron "core". The results are aected by the spacecraft potential and the photo-electron contamination, which we need to characterize in detail in future analyses.

Item Type: Article
Additional Information: Funding information: Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA. Solar Orbiter Solar Wind Analyser (SWA) data are derived from scientific sensors which have been designed and created, and are operated under funding provided in numerous contracts from the UK Space Agency (UKSA), the UK Science and Technology Facilities Council (STFC), the Agenzia Spaziale Italiana (ASI), the Centre National d’Etudes Spatiales (CNES, France), the Centre National de la Recherche Scientifique (CNRS, France), the Czech contribution to the ESA PRODEX programme and NASA. Solar Orbiter SWA work at UCL/MSSL is currently funded under STFC grants ST/T001356/1 and ST/S000240/1. G.N., R.T.W., C.J.O. and D.V. are supported by the STFC Consolidated Grant to UCL/MSSL, ST/S000240/1. D.V. is supported by STFC Ernest Rutherford Fellowship ST/P003826/1.
Uncontrolled Keywords: Instrumentation: miscellaneous, Methods: data analysis, Sun: heliosphere, solar wind, Plasmas
Subjects: F300 Physics
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 23 Nov 2021 14:12
Last Modified: 21 Jan 2022 15:00

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