EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Transmission of foreshock waves through Earth's bow shock

Lucile Turc1, Owen W. Roberts2, Daniel Verscharen3, Andrew P. Dimmock4, Primoz Kajdic5, Minna Palmroth1,6, Yann Pfau-Kempf1, Andreas Johlander7, Maxime Dubart1, Emilia K.J. Kilpua1, Kazue Takahashi8, Naoko Takahashi9,10, Markus Battarbee1, and Urs Ganse1
Lucile Turc et al.
  • 1University of Helsinki, Faculty of Science, Department of Physics, Helsinki, Finland (
  • 2Space Research Institute, Austrian Academy of Sciences, Graz, Austria
  • 3Mullard Space Science Laboratory, University College London, Dorking, UK
  • 4Swedish Institute of Space Physics, Uppsala, Sweden
  • 5Departamento de Ciencias Espaciales, Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico City, Mexico
  • 6Finnish Meteorological Institute, Helsinki, Finland
  • 7Institute of Atmospheric Physics, Czech Academy of Sciences, Prague, Czech Republic
  • 8The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
  • 9Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Tokyo, Japan
  • 10Radio Research Institute, National Institute of Information and Communication Technology, Tokyo, Japan

The foreshock, extending upstream of the quasi-parallel shock and populated with shock-reflected particles, is home to intense wave activity in the ultra-low frequency range. The most commonly observed of these waves are the '30-second' waves, fast magnetosonic waves propagating sunward in the plasma rest frame, but carried earthward by the faster solar wind flow. These waves are thought to be the main source of Pc3 magnetic pulsations (10-45 s periods) in the dayside magnetosphere, but how the waves can transmit through the bow shock and across the magnetosheath had remained unclear. Global hybrid-Vlasov simulations performed with the Vlasiator model provide us with the global view of foreshock wave transmission across near-Earth space. We find that the foreshock waves modulate the plasma parameters just upstream of the bow shock, which in turn periodically changes the shock compression ratio and the downstream pressure. This launches fast-mode waves propagating through the magnetosheath all the way to the magnetopause, where they can further transmit into the dayside magnetosphere. We compare our numerical results with MMS observations near the subsolar point, where we identify earthward-propagating fast-mode waves at the same period as the foreshock waves, consistent with our simulation results. Our findings show that the wave propagation across the bow shock is much more complex than the simple direct transmission of the foreshock waves which was inferred in early studies.

How to cite: Turc, L., Roberts, O. W., Verscharen, D., Dimmock, A. P., Kajdic, P., Palmroth, M., Pfau-Kempf, Y., Johlander, A., Dubart, M., Kilpua, E. K. J., Takahashi, K., Takahashi, N., Battarbee, M., and Ganse, U.: Transmission of foreshock waves through Earth's bow shock, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-6637,, 2023.