EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Solar Orbiter observations of magnetic Kelvin-Helmholtz waves in the solar wind

Rungployphan Kieokaew1, Benoit Lavraud1,2, David Ruffolo3, William Matthaeus4, Yan Yang5, Julia Stawarz6, Sae Aizawa1, Philippe Louarn1, Alexis Rouillard1, Vincent Génot1, Andrey Fedorov1, Rui Pinto1,7, Claire Foullon8, Christopher Owen9, and Timothy Horbury6
Rungployphan Kieokaew et al.
  • 1Institut de Recherche en Astrophysique et Planétologie (IRAP), UPS, CNRS, CNES, Toulouse, France
  • 2Laboratoire d'Astrophysique de Bordeaux, Univ. Bordeaux, 33615 Pessac, France
  • 3Department of Physics, Faculty of Science, Mahidol University, Bangkok, Thailand
  • 4Department of Physics and Astronomy and Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
  • 5Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People’s Republic of China
  • 6Space and Atmospheric Physics, Department of Physics, Blackett Laboratory, Imperial College London, London, UK SW7 2AZ
  • 7Laboratoire Dynamique des Etoiles, des (Exo)planètes et de leur Environnement (LDE3), CEA Saclay, 91191 Gif-sur-Yvette, France
  • 8CGAFD, Mathematics, CEMPS, University of Exeter, Exeter, UK
  • 9Department of Space and Climate Physics, University College London, Mullard Space Science Laboratory, Holmbury St., Mary RH5 6NT, UK

The Kelvin-Helmholtz instability (KHI) is a nonlinear shear-driven instability that develops at the interfaces between shear flows in plasmas. KHI is ubiquitous in plasmas and has been observed in situ at planetary interfaces and at the boundaries of coronal mass ejections in remote-sensing observations. KHI is also expected to develop at flow shear interfaces in the solar wind, but while it was hypothesized to play an important role in the mixing of plasmas and exciting solar wind fluctuations, its direct observation in the solar wind was still lacking. We report first in-situ observations of ongoing KHI in the solar wind using Solar Orbiter during its cruise phase. The KHI is found in a shear layer in the slow solar wind near the Heliospheric Current Sheet. We find that the observed conditions satisfy the KHI onset criterion from linear theory and the steepening of the shear boundary layer is consistent with the development of KH vortices. We further investigate the solar wind source of this event to understand the conditions that support KH growth. In addition, we set up a local MHD simulation using the empirical values to reproduce the observed KHI. This observed KHI in the solar wind provides robust evidence that shear instability develops in the solar wind, with obvious implications in the driving of solar wind fluctuations and turbulence. The reasons for the lack of previous such measurements are also discussed.

How to cite: Kieokaew, R., Lavraud, B., Ruffolo, D., Matthaeus, W., Yang, Y., Stawarz, J., Aizawa, S., Louarn, P., Rouillard, A., Génot, V., Fedorov, A., Pinto, R., Foullon, C., Owen, C., and Horbury, T.: Solar Orbiter observations of magnetic Kelvin-Helmholtz waves in the solar wind, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5247,, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.