TY  - JOUR
A1  - Nishikawa, Ken-Ichi
A1  - Hardee, P.
A1  - Zhang, B.
A1  - Dutan, I.
A1  - Medvedev, M.
A1  - Choi, E. J.
A1  - Min, K. W.
A1  - Niemiec, J.
A1  - Mizuno, Y.
A1  - Nordlund, Ake
A1  - Frederiksen, Jacob Trier
A1  - Sol, H.
A1  - Pohl, Martin
A1  - Hartmann, D. H.
T1  - Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability
JF  - Annales geophysicae
N2  - We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin-Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin-Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field E-z, perpendicular to the flow boundary, and the magnetic field B-y, transverse to the flow direction. After the B-y component is excited, an induced electric field E-x, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios m(i)/m(e) = 1836 and m(i)/m(e) = 20 are similar. In our simulations in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (gamma(j) = 1.5) is larger than for a relativistic jet case (gamma(j) = 15).
KW  - Solar physics
KW  - astrophysics
KW  - astronomy (Energetic particles)
Y1  - 2013
U6  - https://doi.org/10.5194/angeo-31-1535-2013
SN  - 0992-7689
VL  - 31
IS  - 9
SP  - 1535
EP  - 1541
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - GEN
A1  - Nishikawa, K.-I.
A1  - Zhang, B.
A1  - Choi, E. J.
A1  - Min, K. W.
A1  - Niemiec, J.
A1  - Medvedev, M.
A1  - Hardee, P.
A1  - Mizuno, Y.
A1  - Nordlund, A.
A1  - Frederiksen, J.
A1  - Sol, H.
A1  - Pohl, Martin
A1  - Hartmann, D. H.
A1  - Fishman, G.J.
T1  - Radiation from accelerated particles in shocks
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs in the shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and for particle acceleration. These magnetic fields contribute to the electron’s transverse eflection behind the shock. The “jitter” radiation from deflected electrons in turbulent magnetic fields has properties different from synchrotron radiation calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure of gamma-ray bursts, relativistic jets in general, and supernova remnants. In order to calculate radiation from first principles and go beyond the standard synchrotron model, we have used PIC simulations. We present synthetic spectra to compare with the spectra obtained from Fermi observations.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 600 
KW  - relativistic jets
KW  - Weibel instability
KW  - magnetic field generation
KW  - particle acceleration
KW  - radiation
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413128
SN  - 1866-8372
IS  - 600
SP  - 371
EP  - 372
ER  -