Hybrid Simulation of Magnetosheath Jet-Driven Bow Waves

High-speed jets (HSJs) are commonly observed in the Earth's magnetosheath. The HSJs can drive shock-like bow waves when compressing the ambient plasma, which are important for the HSJ's evolution and the energization of charged particles. Here we present the first two-dimensional hybrid simulation of the formation and evolution of jet-driven bow waves. The simulated bow waves exhibit localized enhanced magnetic field and ion density, with their peaks separated by the order of ion inertial length. The bow waves are formed when a super-magnetosonic HSJ encounters a magnetic structure with the magnetic field nearly perpendicular to the HSJ's velocity. The magnetic field structure acts as an obstacle to deflect and decelerate the jet, causing the pile up of ions on the jet side and the compression of the magnetic structure on the downstream side. Our study explains the observed properties of bow waves, and helps to better understand the evolution of HSJs. When the solar wind interacts with the Earth's magnetic field, it creates a bow shock in front of the magnetosphere. The bow shock slows down and heats up the solar wind plasma, creating a turbulent area known as the magnetosheath. Sometimes, high-speed jets (HSJ), observed as high velocity and density pulses, are detected in the magnetosheath. The HSJs can transfer the solar wind plasma through the magnetosheath and potentially affect the near-Earth space where satellites orbit. Recent studies have found that the HSJs can drive shock-like bow waves at their front. The bow waves can accelerate and heat up plasma, similar to the primary shock wave, and they play an important role in the evolution of the HSJs. In this study, we present the first simulation result concerning the formation and evolution of the bow waves, which will help us to better understand the HSJs and the magnetosheath dynamics. We study the formation and evolution of jet-driven bow waves with the two-dimensional hybrid model for the first time Plasma piles up at the ramp of compressed magnetic field, causing separated peaks of density and magnetic field at the bow wave The magnetic field structure acts as an obstacle to decelerate jet, causing the pile up of jet ions at the leading edge