EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Magnetic structures and reformation at quasi-parallel shocks

Andreas Johlander1, Markus Battarbee1, Lucile Turc1, Yann Pfau-Kempf1, Urs Ganse1, Maxime Grandin1, Maxime Dubart1, Markku Alho1, Maarja Bussov1, Harriet George1, Vertti Tarvus1, Konstantinos Papadakis1, Jonas Suni1, Hongyang Zhou1, and Minna Palmroth1,2
Andreas Johlander et al.
  • 1Department of Physics, University of Helsinki, Finland (
  • 2Space and Earth Observation Centre, Finnish Meteorological Institute, Helsinki, Finland

Shock waves in collisionless plasmas are common in heliospheric and astrophysical settings and are some of the most efficient particle accelerators in space. Shocks can undergo self-reformation where a new shock front appears in front of the previous shock front. Shock reformation has been observed previously in both spacecraft observations and simulations, but the process is not yet fully understood. We here study self-reformation of Earth's quasi-parallel bow shock with observations from the four MMS spacecraft and simulation results from the hybrid-Vlasov simulation Vlasiator. We find, in both observations and simulation, that short large amplitude magnetic structures (SLAMS) can constitute shock reformation. The SLAMS form upstream of the shock and grow in amplitude while being convected towards the shock and eventually forming the new shock front. Using MMS's and Vlasiator's high-cadence field and ion measurements, we study how the shock reformation process influences the dynamics and acceleration of ions at the quasi-parallel shock.

How to cite: Johlander, A., Battarbee, M., Turc, L., Pfau-Kempf, Y., Ganse, U., Grandin, M., Dubart, M., Alho, M., Bussov, M., George, H., Tarvus, V., Papadakis, K., Suni, J., Zhou, H., and Palmroth, M.: Magnetic structures and reformation at quasi-parallel shocks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14776,, 2021.


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