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The Rosetta Mission to Comet 67P/ Churyumov-Gerasimenko : Needs for SWMF Modeling

The Rosetta Mission to Comet 67P/ Churyumov-Gerasimenko : Needs for SWMF Modeling. K.C. Hansen Zhenguang Huang. University of Michigan. SWMF User Meeting, October 13-14, 2014. Comet Modeling at UM. ICES Tools Andre Bieler Jeff Kopmanis K.C. Hansen Tamas Gombosi

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The Rosetta Mission to Comet 67P/ Churyumov-Gerasimenko : Needs for SWMF Modeling

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  1. The Rosetta Mission to Comet 67P/Churyumov-Gerasimenko: Needs for SWMF Modeling K.C. Hansen Zhenguang Huang University of Michigan SWMF User Meeting, October 13-14, 2014

  2. Comet Modeling at UM • ICES Tools • Andre Bieler • Jeff Kopmanis • K.C. Hansen • TamasGombosi • Plasma/Neutrals – SWMF • Zhenguang Huang • YinsiShou • Gabor Toth • Martin Rubin (Univ. Bern) • XianzheJia • K.C. Hansen • TamasGombosi • Gas & Dust – AMPS/DSMC • Nicolas Fougere • Andre Bieler • ValeriyTenishev • Mike Combi

  3. 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 cavity

  4. Rosetta Mission • ESA led mission with substantial US participation • Comet 67P/Churyumov-Gerasimenko • Orbiter (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, 2014 • UM Co-I role • Rosina – Rosetta Orbiter Spectrometer for Ion and Neutral Analysis spectrometer • VIRTIS - Visible and Infrared Mapping Spectrometer • RPC - Rosetta Plasma Consortium

  5. Observed Modeling Needs • Modeling during the early mission phases • Landing of Philea is a critical mission element • Neutrals and plasma are very low density • Ability to model the region very near the comet (<200km) • Early mission will spend significant time < 50 km • Later mission will remain within 200-300 km • First images revealed a shape that is VERY non-spherical • Shape just became a much more important factor to model

  6. Resulting Numerical Needs • Fluid Model of the Neutrals • Low density • Fast numerical turn around due to non-steady nature of the comet • Coupled Neutrals and Plasma • Nature of comet shape dictates that the neutrals near the comet will be very non-uniform • Plasma is a result of mass loading the neutrals • Clear that the two cannot be modeled independently for this case • Multi-fluid Hall MHD • Low plasma densities mean that standard MHD may not technically be reliable • Ability to model irregular body shape in BATSRUS/SWMF • Shape 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 properties

  7. 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.

  8. Multi-Fluid Hall Results for Giotto @ Halley

  9. Multi-Fluid Hall Results for Giotto @ Halley

  10. Multi-fluid MHD vs. Hybrid

  11. Cometary neutral and plasma environment simulations with RMOC shape model • Setting the comet shape in the simulation: • Cell center within the shape: body cell • Cell center outside the shape: true cell • Illumination is considered • Inner boundary conditions are specified at the face boundary

  12. Cometary neutral and plasma environment simulations with RMOC shape model • Inner 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. • Outer boundary: open boundary condition Hydrodynamic equations for cometary neutrals

  13. Cometary neutral and plasma environment simulations with RMOC shape model AMPS BATSRUS/SWMF Comparison of neutral density from AMPS & BATS-R-US

  14. Cometary neutral and plasma environment simulations with RMOC shape model AMPS BATSRUS/SWMF Comparison of bulk velocity from AMPS & BATS-R-US

  15. Cometary neutral and plasma environment simulations with RMOC shape model Comparison of neutral density from the simulation and COPS

  16. Cometary neutral and plasma environment simulations with RMOC shape model • The neutral and plasma fluids are coupled. MHD equations for cometary heavy ions, solar wind protons, and electrons

  17. Cometary neutral and plasma environment simulations with RMOC shape model

  18. Conclusions and future work Multi-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.

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