A robust method for handling low density regions in hybrid simulations for collisionless plasmas

A robust method to handle vacuum and near vacuum regions in hybrid simulations for space and astrophysical plasmas is presented. The conventional hybrid simulation model dealing with kinetic ions and a massless charge-neutralizing electron fluid is known to be susceptible to numerical instability due to divergence of the whistler-mode wave dispersion, as well as division-by-density operation in regions of low density. Consequently, a pure vacuum region is not allowed to exist in the simulation domain unless some ad hoc technique is used. To resolve this difficulty, an alternative way to introduce finite electron inertia effect is proposed. Contrary to the conventional method, the proposed one introduces a correction to the electric field rather than the magnetic field. It is shown that the generalized Ohm's law correctly reduces to Laplace's equation in a vacuum which therefore does not involve any numerical problems. In addition, a variable ion-to-electron mass ratio is introduced to reduce the phase velocity of high frequency whistler waves at low density regions so that the stability condition is always satisfied. It is demonstrated that the proposed model is able to handle near vacuum regions generated as a result of nonlinear self-consistent development of the system, as well as pure vacuum regions set up at the initial condition, without losing the advantages of the standard hybrid code.

[1]  Jörg Büchner,et al.  Space Plasma Simulation , 2003 .

[2]  Eric J. Horowitz,et al.  QN3D: A three-dimensional quasi-neutral hybrid particle-in-cell code with applications to the tilt mode instability in field reversed configurations , 1989 .

[3]  M. Goldstein,et al.  An instability of finite amplitude circularly polarized Alfven waves. [in solar wind and corona , 1978 .

[4]  D. Winske,et al.  Diffuse ions produced by electromagnetic ion beam instabilities. [in earth's bow shock , 1984 .

[5]  Charles C. Goodrich,et al.  The structure of perpendicular bow shocks , 1982 .

[6]  James Drake,et al.  Structure of the dissipation region during collisionless magnetic reconnection , 1998 .

[7]  Dan Winske,et al.  Kinetic quasi-viscous and bulk flow inertia effects in collisionless magnetotail reconnection , 1998 .

[8]  Yoshifumi Futaana,et al.  The interaction between the Moon and the solar wind , 2011, Earth, Planets and Space.

[9]  Masahiro Hoshino,et al.  The relation between ion temperature anisotropy and formation of slow shocks in collisionless magnetic reconnection , 2012, 1201.4213.

[10]  Riku Jarvinen,et al.  A new 3‐D spherical hybrid model for solar wind interaction studies , 2013 .

[11]  Petr Hellinger,et al.  Structure of Mercury's magnetosphere for different pressure of the solar wind: Three dimensional hybrid simulations , 2006 .

[12]  D. Winske,et al.  HYBRID CODES: PAST, PRESENT AND FUTURE , 2001 .

[13]  H. Shinagawa,et al.  Global hybrid simulation of the Kelvin–Helmholtz instability at the Venus ionopause , 2002 .

[14]  William M. Farrell,et al.  A simple simulation of a plasma void: Applications to Wind observations of the lunar wake , 1998 .

[15]  M. Holmstrom.  Handling vacuum regions in a hybrid plasma solver , 2013 .

[16]  Xueliang Li,et al.  On a Relation Between , 2012 .

[17]  Tohru Hada,et al.  Decay instability of finite-amplitude circularly polarized Alfven waves - A numerical simulation of stimulated Brillouin scattering , 1986 .

[18]  D. W. Hewett,et al.  A global method of solving the electron-field equations in a zero-inertia-electron-hybrid plasma simulation code , 1980 .

[19]  Dan Winske,et al.  Hybrid simulations of collisionless reconnection in current sheets , 1994 .

[20]  Antonius Otto,et al.  Structure of an MHD‐scale Kelvin‐Helmholtz vortex: Two‐dimensional two‐fluid simulations including finite electron inertial effects , 2008 .

[21]  Douglas S. Harned,et al.  Quasineutral hybrid simulation of macroscopic plasma phenomena , 1982 .

[22]  Pekka Janhunen,et al.  Modelling the solar wind interaction with Mercury by a quasi-neutral hybrid model , 2003 .

[23]  H. K. Wong,et al.  Parametric instabilities of circularly polarized Alfvén waves including dispersion , 1986 .

[24]  Sandra C. Chapman,et al.  Detailed structure and dynamics in particle-in-cell simulations of the lunar wake , 2001 .

[25]  Alexander S. Lipatov,et al.  The Hybrid Multiscale Simulation Technology: An Introduction with Application to Astrophysical and Laboratory Plasmas , 2010 .

[26]  M. Fujimoto,et al.  Ion dynamics and resultant velocity space distributions in the course of magnetotail reconnection , 1998 .