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Computational Modeling Capabilities for Neutral Gas Injection

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.

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Computational Modeling Capabilities for Neutral Gas Injection

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  1. 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

  2. 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

  3. 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)

  4. 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)

  5. 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

  6. Electromagnetic Hybrid PIC • Governing Equations: Electrons: Ions: • Code Formulation (Winski and Omidi, 1993): • Ions: macro-particles; Electrons: massless fluid • Maxwell’s equation in the low frequency approximation • Quasi-neutral plasma

  7. Selected Relevant Previous Studies: Release Experiments in Space • 3-D EM Full Particle PIC-MCC Simulations of Critical Ionization Velocity Experiment in Space (Wang et al., JGR, 101A(1), 1996)

  8. 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

  9. Selected Relevant Previous Studies: Micro-Instabilities in Space Plasmas • EM Hybrid PIC Simulations of Electromagnetic Heavy Ion/Proton Instabilities (Wang et al., JGR, 104(A11), 1999) • EM Full Particle PIC Simulations of Whistler Instabilities and Electron Anisotropy Upper Bound (Gary and Wang, JGR, 101(A5), 1996)

  10. 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

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