67P ChuryumovGerasimenko Needs for SWMF Modeling KC Hansen Zhenguang Huang University of Michigan SWMF User Meeting October 1314 2014 Comet Modeling at UM ICES Tools Andre Bieler ID: 242858
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Slide1
The Rosetta Mission to Comet 67P/Churyumov-Gerasimenko: Needs for SWMF Modeling
K.C. HansenZhenguang Huang
University of Michigan
SWMF User Meeting, October 13-14, 2014Slide2
Comet Modeling at UM
ICES Tools
Andre
Bieler
Jeff
Kopmanis
K.C. Hansen
Tamas
Gombosi
Plasma/Neutrals – SWMF
Zhenguang
Huang
Yinsi
Shou
Gabor
Toth
Martin Rubin (Univ. Bern)
Xianzhe
Jia
K.C. Hansen
Tamas
Gombosi
Gas & Dust – AMPS/
DSMC
Nicolas
Fougere
Andre
Bieler
Valeriy
Tenishev
Mike
CombiSlide3
Comet-Solar Wind Interaction
Mass Loading
Extends millions of km upstream
Major contributor to structure and dynamics
Leads to major comet challenge of resolving multiple length scales
Solar Wind
Greatly slowed due to mass loading upstream of the comet
Low Mach number shock due to mass loading
Multiple separating surfaces
Bow shock
Diamagnetic cavity
Inner shock
Low mass loading regime
Shock -> Mach cone
Mach cone may touch body
No-diamagnetic cavitySlide4
Rosetta MissionESA led mission with substantial US participationComet 67P/Churyumov-GerasimenkoOrbiter (
Rosettta)Follows the comet from 3.5AU until just after perihelion (nominal mission)20-200 km “orbits”Aug 2014 – Dec 2015
Lander (Philae)Planned to land on November 12, 2014UM Co-I role
Rosina – Rosetta Orbiter Spectrometer for Ion and Neutral Analysis spectrometer VIRTIS - Visible and Infrared Mapping
SpectrometerRPC - Rosetta Plasma ConsortiumSlide5
Observed Modeling NeedsModeling during the early mission phasesLanding of Philea is a critical mission element
Neutrals and plasma are very low densityAbility to model the region very near the comet (<200km)
Early mission will spend significant time < 50 kmLater mission will remain within 200-300 kmFirst images revealed a shape that is VERY non-spherical
Shape just became a much more important factor to modelSlide6
Resulting Numerical NeedsFluid Model of the NeutralsLow densityFast numerical turn around due to non-steady nature of the comet
Coupled Neutrals and PlasmaNature of comet shape dictates that the neutrals near the comet will be very non-uniformPlasma is a result of mass loading the neutralsClear that the two cannot be modeled independently for this caseMulti-fluid Hall MHD
Low plasma densities mean that standard MHD may not technically be reliableAbility to model irregular body shape in BATSRUS/SWMFShape is likely to greatly influence the near body neutral and plasma distribution
Sources on the body should be able to be calculated using illumination and other propertiesSlide7
Multi-Fluid Hall Results for Giotto @ Halley
One of the major advantages of this model is the self consistent calculation of the electron temperatures. The electron temperature at comets can play a major role in the location of ion-boundaries and other
cometary
features.Slide8
Multi-Fluid Hall Results for Giotto @ Halley Slide9
Multi-Fluid Hall Results for Giotto @ Halley Slide10
Multi-fluid MHD vs. HybridSlide11
Cometary neutral and plasma environment simulations with RMOC shape modelSetting the comet shape in the simulation:Cell center within the shape: body cell
Cell center outside the shape: true cellIllumination is considered
Inner boundary conditions are specified at the face boundarySlide12
Cometary neutral and plasma environment simulations with RMOC shape model
Hydrodynamic equations for cometary neutrals
I
nner boundary: neutral density, velocity and temperature match the mass and energy flux of a half-
maxwellian
particle distribution. the number density flux and the temperature varies as a function of the solar zenith angle relative to the shape model’s triangular faces. the outflow velocity is in the direction of the normal of the triangulated surface.
O
uter boundary: open boundary conditionSlide13
Cometary neutral and plasma environment simulations with RMOC shape model
Comparison of neutral density from AMPS & BATS-R-US
AMPS
BATSRUS/SWMFSlide14
Cometary neutral and plasma environment simulations with RMOC shape model
Comparison of bulk velocity from AMPS & BATS-R-US
AMPS
BATSRUS/SWMFSlide15
Cometary neutral and plasma environment simulations with RMOC shape model
Comparison of neutral density from the simulation and COPSSlide16
Cometary neutral and plasma environment simulations with RMOC shape model
MHD equations for cometary heavy ions, solar wind protons, and electrons
The neutral and plasma fluids are coupled.Slide17
Cometary neutral and plasma environment simulations with RMOC shape modelSlide18
Conclusions and future workMulti-fluid Hall MHD simulations agree well with Hybrid simulations. The
first coupled hydrodynamic and MHD simulation of a comet.The first realistic simulation with a shape model.Neutral results agree well with COPS
data.Compare plasma results with RPC
data.Simulate the neutral and plasma environment at different heliocentric locations
.