Magnetic increases with central current sheets: observations with Parker Solar Probe

¹ Institut de Recherche en Astrophysique et Planétologie, CNRS, UPS, CNES, Toulouse, France
e-mail: nfargette@irap.omp.eu
² The Blackett Laboratory, Department of Physics, Imperial College London, London, UK
³ Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA, USA
⁴ Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA
⁵ Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA
⁶ Laboratoire de Physique des Plasmas, CNRS, Sorbonne Universite, Ecole Polytechnique, Observatoire de Paris, Universite Paris-Saclay, Paris, France
⁷ Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, USA
⁸ Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA
⁹ Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
¹⁰ Solar System Exploration Division, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
¹¹ School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
¹² LPC2E, CNRS and University of Orléans, 3 Avenue de la Recherche Scientifique, 45071 Orléans, France

Received: 15 August 2020
Accepted: 23 October 2020

Abstract

Aims. We report the observation by Parker Solar Probe (PSP) of magnetic structures in the solar wind that present a strong peak in their magnetic field magnitude with an embedded central current sheet. Similar structures have been observed, either at the Earth’s magnetopause and called interlinked flux tubes, or in the solar wind and called interplanetary field enhancements.

Methods. In this work, we first investigate two striking events in detail; one occurred in the regular slow solar wind on November 2, 2018 and the other was observed during a heliospheric current sheet crossing on November 13, 2018. They both show the presence of a central current sheet with a visible ion jet and general characteristics consistent with the occurrence of magnetic reconnection. We then performed a survey of PSP data from encounters 1 to 4 and find 18 additional events presenting an increase in the magnetic field magnitude of over 30% and a central current sheet. We performed a statistical study on the 20 “magnetic increases with central current sheet” (MICCS), with 13 observed in the regular slow solar wind with a constant polarity (i.e., identical strahl direction), and 7 which were specifically observed near a heliospheric current sheet crossing.

Results. We analyze and discuss the general properties of the structures, including the duration, location, amplitude, and magnetic topology, as well as the characteristics of their central current sheet. We find that the latter has a preferential orientation in the TN plane of the RTN frame. We also find no significant change in the dust impact rate in the vicinity of the MICCS under study, leading us to conclude that dust probably plays no role in the MICCS formation and evolution. Our findings are overall consistent with a double flux tube-configuration that would result from initially distinct flux tubes which interact during solar wind propagation.