High-cadence measurements of electron pitch-angle distributions from Solar Orbiter SWA-EAS burst mode operations

Owen, C. J., Kataria, D. O., Bercic, L., Horbury, T. S., Berthomier, M., Verscharen, D., Bruno, R., Livi, S., Louarn, P., Anekallu, C., Kelly, C. W., Lewis, G. R., Watson, G., Fortunato, V., Mele, G., Nicolaou, G., Wicks, Robert, O'Brien, H., Evans, V. and Angelini, V. (2021) High-cadence measurements of electron pitch-angle distributions from Solar Orbiter SWA-EAS burst mode operations. Astronomy & Astrophysics, 656. L9. ISSN 0004-6361

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Official URL: https://doi.org/10.1051/0004-6361/202140959


Small-scale kinetic processes associated with turbulence, plasma instabilities, magnetic reconnection, etc., play a major role in dissipating energy and governing the large-scale evolution of the solar wind. However, a general impediment to improving the understanding of the kinetic physics of the solar wind is in the limitations on measurement cadences of particle instruments, which are usually several orders of magnitude below the equivalent cadences of field instruments. Nevertheless, knowledge of the details of the particle velocity distribution functions (VDFs) at sub-second cadence is required to make progress in this area. This is particularly true for the electron VDFs, which play a significant role in the overall energetics of the solar wind through their transmission of heat flux from the Sun. In this paper, we detail and illustrate a novel measurement scheme deployed on Solar Orbiter’s Solar Wind Analyser Electron Analyser System (SWA-EAS), which allows for 2D pitch angle distributions (PAD) to be returned over short periods (5–10 min) at a cadence of 0.125 s. This is achieved through the use of a B-field vector shared by the magnetometer (MAG) instrument to steer the SWA-EAS system to record only that part of the full SWA-EAS field-of-view needed to construct the PAD. We provide an example of early observations using this scheme to illustrate that it is working well. Given that the electrons are usually gyrotropic, these measurements provide a new tool with which to derive details of the electron VDFs at high cadence for the study of the solar wind’s kinetic processes.

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. The Solar Orbiter MAG was funded by the UK Space Agency (grant ST/T001062/1). D.V. is supported by STFC Ernest Rutherford Fellowship ST/P003826/1. T.H. is supported by STFC grant ST/S000364/1.
Uncontrolled Keywords: magnetic fields, plasmas, heliosphere, Sun, (Sun:) solar wind
Subjects: F300 Physics
F500 Astronomy
F900 Others in Physical Sciences
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: Rachel Branson
Date Deposited: 23 Nov 2021 12:09
Last Modified: 24 Jan 2022 11:30
URI: http://nrl.northumbria.ac.uk/id/eprint/47816

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