NBIA seminar, Aug.6th. Prof. Ken-Ichi Nishikawa – Niels Bohr Institute - University of Copenhagen

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NBIA seminar, Aug.6th. Prof. Ken-Ichi Nishikawa

Title: Global simulations of relativistic jets with shocks and shear-flow
Dr. Ken-Ichi Nishikawa (Univ. of Alabama, Huntsville, Dept. of Physics)

We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma. Strong magnetic fields generated in the trailing shock contribute to the electrons' transverse deflection and acceleration. The kinetic Kelvin-Helmholtz instability (kKHI) is also responsible to create strong DC and AC magnetic fields. Velocity shears in core-sheath jets create strong transverse magnetic fields, perpendicular to the jet. Simulations where unmagnetized jets are injected into unmagnetized ambient plasmas revealed excitation of the Weibel instability with kKHI and particle acceleration and its ejection from the jets. We will discuss how the Lorentz factors of jets affect the growth rates of kKHI, and the properties of self-consistently calculated radiation from electrons accelerated in these turbulent magnetic fields in the shocks. Mainly, the synthetic spectra depend on the bulk Lorentz factor of the jet, its temperature and strength of the generated magnetic fields. The properties of the calculated emerging radiation and spectra improve our understanding of the physics underlying a most complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

For further information, please contact trier@nbi.ku.dk