Computational Modeling Capabilities for
Neutral Gas Injection
Wayne Scales and Joseph Wang
Space @ Virginia Tech
Center for Space Science and Engineering Research
College of Engineering
Virginia Tech
Blacksburg, Virginia
Objectives
• Develop computational models for artificial plasma cloud creation by neutral gas injection
• Investigate the nonlinear evolution of plasma waves generated by artificial plasma cloud creation that lead to pitch angle scattering of trapped electrons (Ganguli et al., 2007)
• Determine the efficiency of the process in terms of plasma wave energy compared to injected neutral gas kinetic energy
Space @ VT Plasma Simulation Capabilities
• Relevant plasma simulation models available:
– 3-D Electromagnetic Particle-in-Cell (PIC) (full particle)– 3-D Electromagnetic Particle-in-Cell with Monte Carlo Collision (PIC-MCC) (full particle)– 3-D Electromagnetic PIC with Deformable Grids (full particle)
– 3-D Hybrid Electromagnetic PIC (hybrid fluid-particle)– 2-D Hybrid Electromagnetic PIC (hybrid fluid-particle)
– 3-D Electrostatic PIC (full particle/hybrid fluid-particle)– 3-D Electrostatic PIC-MCC (full particle/hybrid fluid-particle)– 3-D Electrostatic Immersed-Finite-Element PIC (IFE-PIC) (full particle/hybrid fluid
particle)– 3-D Electrostatic Hybrid-Grid Immersed-Finite-Element PIC (HG-IFE-PIC) (full
particle/hybrid fluid-particle)
Prior Relevant Experience in Neutral Gas Release/Plasma Cloud Injection in Space
• Modeling of Critical Ionization Velocity (CIV) Experiments
• Modeling of Electron Attachment Chemical Release Experiments
• Modeling of Dust Cloud Releases
• Modeling of Artificial Perpendicular Ion Beam Injections
• Modeling of Micro-Instabilities in Space Plasmas (Heavy Ion/Proton Instability, Ion Cyclotron Instability, Whistler Instability, etc)
Electromagnetic Full Particle PIC and PIC-MCC
• Governing Equations:
• Code Formulation (Wang et al, Computer Physics Comm., 87, 1995):– Finite-difference time-domain solution for EM wave– Particle representation for both ions and electrons (relativistic equation of motion)– Buneman’s rigorous charge conservation scheme for current deposit– Monte-Carlo collision subroutine for charged particle-neutral collision– Implemented on massively parallel supercomputers
Electromagnetic Hybrid PIC
• Governing Equations:
• Code Formulation (Winski and Omidi, 1993):– Ions: macro-particles; Electrons: massless fluid– Maxwell’s equation in the low frequency approximation – Quasi-neutral plasma
Electrons:
Ions:
• 3-D EM Full Particle PIC-MCC Simulations of Critical Ionization Velocity Experiment in Space (Wang et al., JGR, 101A(1), 1996)
Selected Relevant Previous Studies: Release Experiments in Space
• 2-D ES hybrid (PIC-fluid) modeling of plasma turbulence created by dust cloud releases across the geomagnetic field (Scales et al., 2001) resulting from plasma velocity shear instabilities (Ganguli et al., 1992).
electrons
ions
dust
• EM Hybrid PIC Simulations of Electromagnetic Heavy Ion/Proton Instabilities (Wang et al., JGR, 104(A11), 1999)
Selected Relevant Previous Studies: Micro-Instabilities in Space Plasmas
• EM Full Particle PIC Simulations of Whistler Instabilities and Electron Anisotropy Upper Bound (Gary and Wang, JGR, 101(A5), 1996)
Initial Approach:• I: Initial Studies:
– Apply existing hybrid PIC code (zero electron inertia) for preliminary simulations of instabilities generated by the velocity ring distribution– Initial studies on effects of electron model used by hybrid code
• Finite Electron Inertia?• Electron Energy Equation?• Hybrid PIC vs. Full particle PIC?
– Explore the feasibility of applying parallel full particle PIC in this study
• II: Computational Model Modification: – Explore 2 implementation approaches to include finite electron inertia in hybrid codes:
• Lipatov (2001)
• “kinetic” density electron fluid model (Advance electron density and velocities defined at mesh points using a pseudo-particle approach)
• III: Simulation Studies: Consider efficiency of wave generation with the following parameters:
– neutral density– neutral mass
– characteristics of velocity ring distribution