Evolution of Global Relativistic Jets: Collimations and Expansion with kKHI and the Weibel Instability

• Main Authors: Nishikawa, K. I, Frederiksen, J. T, Nordlund, A, Mizuno, Y, Hardee, P. E, Niemiec, J, Gomez, J. L, Pe'er, A, Dutan, I, Meli, A, Sol, H, Pohl, M, Hartman, D. H
• Format: Journal Article
• Language: English
• Published: 04-02-2016
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.1511.03581

ApJ, 820, 94, 2016 One of the key open questions in the study of relativistic jets is their
interaction with the environment. Here, we study the initial evolution of both
electron-proton and electron-positron relativistic jets, focusing on their
lateral interaction with the ambient plasma. We trace the generation and
evolution of the toroidal magnetic field generated by both kinetic
Kelvin-Helmholtz (kKH) and Mushroom instabilities (MI). This magnetic field
collimates the jet. We show that in electron-proton jet, electrons are
perpendicularly accelerated with jet collimation. The magnetic polarity
switches from the clockwise to anti-clockwise in the middle of jet, as the
instabilities weaken. For the electron-positron jet, we find strong mixture of
electron-positron with the ambient plasma, that results in the creation of a
bow shock. Merger of magnetic field current filaments generate density bumps
which initiate a forward shock. The strong mixing between jet and ambient
particles prevents full development of the jet on the studied scale. Our
results therefore provide a direct evidence for both jet collimation and
particle acceleration in the created bow shock. Differences in the magnetic
field structures generated by electron-proton and electron-positron jets may
contribute to observable differences in the polarized properties of emission by
electrons.