Articles | Volume 31, issue 9
Ann. Geophys., 31, 1535–1541, 2013

Special issue: Dynamical processes in space plasmas II

Ann. Geophys., 31, 1535–1541, 2013

Regular paper 06 Sep 2013

Regular paper | 06 Sep 2013

Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

K.-I. Nishikawa1, P. Hardee2, B. Zhang3, I. Duţan4, M. Medvedev5, E. J. Choi6, K. W. Min6, J. Niemiec7, Y. Mizuno8, A. Nordlund9, J. T. Frederiksen9, H. Sol10, M. Pohl11, and D. H. Hartmann12 K.-I. Nishikawa et al.
  • 1Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, 320 Sparkman Drive, ZP12, Huntsville, AL 35805, USA
  • 2Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, AL 35487, USA
  • 3Department of Physics, University of Nevada, Las Vegas, NV 89154, USA
  • 4Institute of Space Science, Atomistilor 409, Bucharest-Magurele 077125, Romania
  • 5Department of Physics and Astronomy, University of Kansas, KS 66045, USA
  • 6Korea Advanced Institute of Science and Technology, Daejeon 305-701, South Korea
  • 7Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
  • 8Institute of Astronomy, National Tsing-Hua University, Hsinchu, Taiwan 30013, Republic of China
  • 9Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
  • 10LUTH, Observatore de Paris-Meudon, 5 place Jules Jansen, 92195 Meudon Cedex, France
  • 11Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam-Golm, Germany
  • 12Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA

Abstract. 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 Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, 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 mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5) is larger than for a relativistic jet case (γj = 15).