EGU General Assembly 2020
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

ULF waves in the foreshock formed by the radial IMF: their effect on solar wind sheath-like deflection

Olga Gutynska1, Jaroslav Urbář2, Jana Šafránková1, and Zdeněk Němeček1
Olga Gutynska et al.
  • 1Charles University, Faculty of Mathematics and Physics, DEpartment of Surface and Plasma Science, Prague, Czechia (
  • 2Institute of Atmospheric Physics, Czech Academy of Sciences, Prague, Czech Republic

Particle reflection at the bow shock provides a source of free energy to drive local instabilities and turbulence within the foreshock. A variety of low-frequency fluctuations (up to 16 mHz) results from the interactions of back-streaming ions with the incoming solar wind flow. We report observations of low-frequency magnetosonic waves observed during intervals of a radial interplanetary magnetic field in the foreshock. A case study of simultaneous dual THEMIS spacecraft observations of asymmetrical fluctuations in Vy is complemented by a statistical study of similar solar wind deflections in the foreshock.  Our moment calculations do not include the reflected particles as well as heavier ions, revealed the modulation of a solar wind core and deflection of the solar wind in the foreshock. This effect decreases with the distance from the bow shock. We conclude that large asymmetrical Vy velocity component fluctuations are typical for the foreshock formed by the radial IMF. The asymmetry of fluctuations changes the mean direction of the incoming solar wind flow within the foreshock leading to preconditioning prior to its encounter with the bow shock.

How to cite: Gutynska, O., Urbář, J., Šafránková, J., and Němeček, Z.: ULF waves in the foreshock formed by the radial IMF: their effect on solar wind sheath-like deflection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3687,, 2020.


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