1. K.C. H ANSEN Z HENGUANG H UANG University of Michigan SWMF User Meeting, October 13-14, 2014

2. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 ICES T OOLS  Andre Bieler  Jeff Kopmanis  K.C. Hansen  Tamas Gombosi P LASMA /N EUTRALS – SWMF  Zhenguang Huang  Yinsi Shou  Gabor Toth  Martin Rubin (Univ. Bern)  Xianzhe Jia  K.C. Hansen  Tamas Gombosi G AS & D UST – AMPS/DSMC  Nicolas Fougere  Andre Bieler  Valeriy Tenishev  Mike Combi

3. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 M ASS L OADING  Extends millions of km upstream  Major contributor to structure and dynamics  Leads to major comet challenge of resolving multiple length scales S OLAR W IND  Greatly slowed due to mass loading upstream of the comet  Low Mach number shock due to mass loading M ULTIPLE SEPARATING SURFACES  Bow shock  Diamagnetic cavity  Inner shock L OW MASS LOADING REGIME  Shock -> Mach cone  Mach cone may touch body  No-diamagnetic cavity

4. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 ESA LED MISSION WITH SUBSTANTIAL US PARTICIPATION C OMET 67P/C HURYUMOV -G ERASIMENKO O RBITER (R OSETTTA )  Follows the comet from 3.5AU until just after perihelion (nominal mission)  20-200 km “orbits”  Aug 2014 – Dec 2015 L ANDER (P HILAE )  Planned to land on November 12, 2014 UM C O -I ROLE  Rosina – Rosetta Orbiter Spectrometer for Ion and Neutral Analysis spectrometer  VIRTIS - Visible and Infrared Mapping Spectrometer  RPC - Rosetta Plasma Consortium

5. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 M ODELING DURING THE EARLY MISSION PHASES  Landing of Philea is a critical mission element  Neutrals and plasma are very low density A BILITY TO MODEL THE REGION VERY NEAR THE COMET (<200 KM )  Early mission will spend significant time < 50 km  Later mission will remain within 200-300 km F IRST IMAGES REVEALED A SHAPE THAT IS VERY NON - SPHERICAL  Shape just became a much more important factor to model

6. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 F LUID M ODEL OF THE N EUTRALS  Low density  Fast numerical turn around due to non-steady nature of the comet C OUPLED N EUTRALS AND P LASMA  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 M ULTI - FLUID H ALL MHD  Low plasma densities mean that standard MHD may not technically be reliable A BILITY 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. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 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. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014

11. 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. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 Hydrodynamic equations for cometary neutrals 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

13. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 Comparison of neutral density from AMPS & BATS-R-US AMPSBATSRUS/SWMF

14. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 Comparison of bulk velocity from AMPS & BATS-R-US AMPSBATSRUS/SWMF

15. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 Comparison of neutral density from the simulation and COPS

16. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014 MHD equations for cometary heavy ions, solar wind protons, and electrons The neutral and plasma fluids are coupled.

17. SWMF User Meeting K.C. Hansen, Zhenguang Huang October 13-14, 2014

18. 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.