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

Large amplitude ion-acoustic waves observed in the solar wind by the Solar Orbiter

David Pisa1, Jan Soucek1, Ondrej Santolik1,2, Milan Maksimovic3, Timothy Horbury4, Christopher Owen5, and the SolO RPW, MAG, and SWA instrument teams*
David Pisa et al.
  • 1Institute of Atmospheric Physics of the Czech Academy of Sciences, Prague 4, Czechia (
  • 2Faculty of Mathematics and Physics, Charles University, Prague, Czechia
  • 3LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Meudon, France
  • 4Department of Physics, Imperial College London, London SW7 2AZ, UK
  • 5Mullard Space Science Laboratory, University College London, UK
  • *A full list of authors appears at the end of the abstract

Electric field observations of the Time Domain Sampler (TDS) receiver, a part of the Radio and Plasma Waves (RPW) instrument onboard Solar Orbiter, often exhibit very intense broadband emissions at frequencies below 10 kHz in the spacecraft frame. The RPW instrument has been operating almost continuously during the commissioning phase of the mission from March to May, the first perihelion in June, and through the first flyby of Venus in late December 2020. Nearly a year of observations allow us to perform a statistical study of ion-acoustic waves in the solar wind covering an interval of heliocentric distances between 0.5 AU to 1 AU. The occurrence of low-frequency waves peaks around perihelion in June at distances of 0.5 AU and decreases with increasing distances, with only a few waves detected per day in late September at ~1 AU. A more detailed analysis of triggered waveform snapshots shows the typical wave frequency at about 3 kHz and wave power about 5e-2 mV2/m2. The distribution of the relative phase between two components of the projected E-field in the Spacecraft Reference Frame (SRF) shows a mostly linear wave polarization. These waves are interpreted as strongly Doppler-shifted ion-acoustic waves, generated by solar wind ion beams and often accompany large-scale solar wind structures. A detailed analysis of the Doppler-shift using solar wind data from a Proton and Alpha particle Sensor (PAS), a part of Solar Wind Analyzer (SWA), is done for several examples.

SolO RPW, MAG, and SWA instrument teams:

RPW: Stuart Bale, Thomas Chust, Yuri Khotyaintsev, Volodya Krasnoselskikh, Matthieu Kretzschmar, Eric Lorfèvre, Dirk Plettemeier, Manfred Steller, Stepan Stverak, Pavel Travnicek, Andris Vaivads, Antonio Vecchio, FGM: Virginia Angelini, Vincent Evans, Helene O'Brien, SWA: Philippe Louarn

How to cite: Pisa, D., Soucek, J., Santolik, O., Maksimovic, M., Horbury, T., and Owen, C. and the SolO RPW, MAG, and SWA instrument teams: Large amplitude ion-acoustic waves observed in the solar wind by the Solar Orbiter, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10023,, 2021.

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