Letter to the Editor

Solar Orbiter observations of the structure of reconnection outflow layers in the solar wind

¹ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
e-mail: c.owen@ucl.ac.uk
² Now at BBC Research & Development, Wood Lane, London W12 7TQ, UK
³ INAF-Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133 Roma, Italy
⁴ Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238, USA
⁵ Institut de Recherche en Astrophysique et Planétologie, 9, Avenue du Colonel Roche, B.P. 4346, 31028 Toulouse Cedex 4, France
⁶ Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau, France
⁷ Space Science Center, University of New Hampshire, Morse Hall, Durham, NH 03824, USA
⁸ Planetek Italia S.r.l., Via Massaua, 12, 70132 Bari, BA, Italy
⁹ Northumbria University, Department of Mathematics, Physics and Electrical Engineering, Newcastle upon Tyne NE1 8QH, UK
¹⁰ Space and Atmospheric Physics, The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK

Received: 30 March 2021
Accepted: 26 September 2021

Abstract

We briefly review an existing model of the structure of reconnection layers which predicts that several more distinct layers, in the form of contact discontinuities, rotational Alfvèn waves, or slow shocks, should be identifiable in solar wind reconnection events than are typically reported in studies of reconnection outflows associated with bifurcated current sheets. We re-examine this notion and recast the identification of such layers in terms of the changes associated with the boundaries of both the ion and electron outflows from the reconnection current layers. We then present a case study using Solar Orbiter MAG and SWA data, which provides evidence consistent with this picture of extended multiple layers around the bifurcated current sheet. A full confirmation of this picture requires more detailed examination of the particle distributions in this and other events. However, we believe this concept is a valuable framework for considering the nature of reconnection layers in the solar wind.