New Publication: “Transmission of foreshock waves through Earth’s bow shock” by Lucile Turc et al.

The Earth’s magnetosphere and its bow shock, which is formed by the interaction of the supersonic solar wind with the terrestrial magnetic field, constitute a rich natural laboratory enabling in situ investigations of universal plasma processes. Under suitable interplanetary magnetic field conditions, a foreshock with intense wave activity forms upstream of the bow shock. So-called 30 s waves, named after their typical period at Earth, are the dominant wave mode in the foreshock and play an important role in modulating the shape of the shock front and affect particle reflection at the shock. These waves are also observed inside the magnetosphere and down to the Earth’s surface, but how they are transmitted through the bow shock remains unknown. By combining state-of-the-art global numerical simulations and spacecraft observations, we demonstrate that the interaction of foreshock waves with the shock generates earthward-propagating, fast-mode waves, which reach the magnetosphere. These findings give crucial insight into the interaction of waves with collisionless shocks in general and their impact on the downstream medium.

a, Colour map of the magnetic field strength fluctuations in the simulation plane at time t = 500 s from the beginning of the simulation. We subtract <B>50s, which is a 50 s average of the field magnitude, from B to reveal the fluctuations of the magnetic field magnitude. The black curve shows the approximate magnetopause location. The black arrows show the IMF direction, and the purple arrows depict the shock normal direction nshock at two positions along the bow shock. b, PSD of the total magnetic field fluctuations at the three locations marked by coloured circles in a. c, PSD of the magnetic field fluctuations parallel and perpendicular to the mean magnetic field at the virtual spacecraft location in the magnetosheath. The perpendicular directions are defined such that B⊥1 lies in the simulation (x–y) plane while B⊥2 completes the right-handed set.

Full Article:
Turc, L., Roberts, O.W., Verscharen, D., Dimmock, A. P. (SHARP) et al. (2022). Transmission of foreshock waves through Earth’s bow shock. Nature Physics, 19, doi: 10.1038/s41567-022-01837-z

License: CC BY 4.0