kinetic modeling of the sheath scale in the lunar plasma environment

Kinetic Modeling of the Sheath Scale in the Lunar Plasma

Environment

Tech-X Corporation5621 Arapahoe Ave., Boulder, CO 80303

http://www.txcorp.com

Peter Messmer*, Keegan Amyx, Peter Stoltz, Andrew Poppe, Mihay Horanyi, Scott

Robertson, Zoltan Sternovsky messmer@txcorp.com

CCLDAS All Hands Meeting, Boulder, CO, July 10, 2009

VORPAL -A Plasma Modeling Framework

Original target applications: Laser Wakefield Acceleration

PIC, Fluid, HybirdElectrostatic, EMMulti-Dimensional (N=1,2,3)Fully parallel

Scaling for > 32,000 PEs Flexible domain decomposition

Broad range of physics features:- Complex geometries- Ionization, recombination, CEX physics- Field ionization

http://www.txcorp.com/products/VORPAL

Code/setup Validation with 1D Photoelectron Sheath

R. Garad & J Tunaley, JGR 76(10), 2498, 1971

A. Poppe & M. Horanyi, WPDP, 2009

2D ES simulation, Y periodic ,200 x 10 cellsdx = 1050 particles per cell nominal

1

00

2

21/

z

EE

31

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2

31/

z

EE

Simulation

Garad&Tunaley

Monoenergetic

Maxwellian

2D Monoenergetic Sheath

2D ES simulation, left wall = 0V200 x 100 cellsElectrons, ProtonsMonoenergetic ,V0 = 200 eV (!)

electrons

protons

Scenario with Surface Charging

Surface-Charging No surface charging

(just for comparison)

2D Thermal Sheath with Surface Charging

2D ES simulation, left wall = 0V200 x 100 cellsElectronsHeavy Protons, Heavy electrons (m/m0= 5000)Vsig = 3eV, Vtherm = 3 eV

Electron impact creates“heavy electrons”

Electrons get absorbed

Electric field mainly due to positive charge of emitting

region

ChargingNon Charging

“Heavy Electrons” follow the electric field lines

2D ES simulation, left wall = 0V200 x 100 cellsElectronsHeavy Protons, Heavy electrons (m/m0= 5000)Vsig = 3eV, Vtherm = 3 eV

Initial 3D simulations

3D ES simulation, bottom wall = 0V10 x 100 x 100 cellsElectronsProtons, Heavy electrons (m/m0= 5000)Vsig = 3eV, Vtherm = 3 eV

Charging of surface

No charging of surface

Summary / Conclusions / Future work

Presented VORPAL simulations of plasma sheath Validated with kinetic theory for 1D sheath Presented 2D simulation with/without surface charging “heavy electrons” move in electrostatic field, follow (curved)

field lines

Future work: Convergence studies, more realistic parameters Inclusion of solar wind Time dependent problems, angular dependency of photo-

currents Complex geometries (crater, habitat, instrument) 3D

Work supported by CCLDAS and Tech-X Corp.