Solar Orbiter’s first Venus flyby

MAG observations of structures and waves associated with the induced Venusian magnetosphere

¹ Space Research Institute, Austrian Academy of Sciences, Graz, Austria
e-mail: martin.volwerk@oeaw.ac.at
² Department of Physics, The Blackett Laboratory, Imperial College London, London, UK
³ Space Sciences Laboratory, University of California, Berkeley, CA, USA
⁴ The Johns Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
⁵ LPP, CNRS, École Polytechnique, Sorbonne Université, Observatoire de Paris, Université Paris-Saclay, PSL Research University, Palaiseau, Paris, France
⁶ Swedish Institute of Space Physics (IRFU), Uppsala, Sweden
⁷ Universidad de Alcalá, Space Research Group, Alcalá de Henares, Spain
⁸ Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Kiel, Germany

Received: 29 March 2021
Accepted: 11 May 2021

Abstract

Context. The induced magnetosphere of Venus is caused by the interaction of the solar wind and embedded interplanetary magnetic field with the exosphere and ionosphere of Venus. Solar Orbiter entered Venus’s magnetotail far downstream, > 70 Venus radii, of the planet and exited the magnetosphere over the north pole. This offered a unique view of the system over distances that had only been flown through before by three other missions, Mariner 10, Galileo, and BepiColombo.

Aims. In this study, we study the large-scale structure and activity of the induced magnetosphere as well as the high-frequency plasma waves both in the magnetosphere and in a limited region upstream of the planet where interaction with Venus’s exosphere is expected.

Methods. The large-scale structure of the magnetosphere was studied with low-pass filtered data and identified events are investigated with a minimum variance analysis as well as combined with plasma data. The high-frequency plasma waves were studied with spectral analysis.

Results. We find that Venus’s magnetotail is very active during the Solar Orbiter flyby. Structures such as flux ropes and reconnection sites were encountered, in addition to a strong overdraping of the magnetic field downstream of the bow shock and planet. High-frequency plasma waves (up to six times the local proton cyclotron frequency) are observed in the magnetotail, which are identified as Doppler-shifted proton cyclotron waves, whereas in the upstream solar wind, these waves appear just below the proton cyclotron frequency (as expected) but are very patchy. The bow shock is quasi-perpendicular, however, expected mirror mode activity is not found directly behind it; instead, there is strong cyclotron wave power. This is most likely caused by the relatively low plasma-β behind the bow shock. Much further downstream, magnetic hole or mirror mode structures are identified in the magnetosheath.