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, 2014

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

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 Combi

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

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

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

ROSETTA MISSION

ESA 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, 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

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

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

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

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

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

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.

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

MULTI-FLUID HALL RESULTS FOR GIOTTO @ HALLEY

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

MULTI-FLUID HALL RESULTS FOR GIOTTO @ HALLEY

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

MULTI-FLUID MHD VS. HYBRID

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

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

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

COMETARY NEUTRAL AND PLASMA ENVIRONMENT SIMULATIONS WITH RMOC

SHAPE MODEL

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

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

COMETARY NEUTRAL AND PLASMA ENVIRONMENT SIMULATIONS WITH RMOC

SHAPE MODEL

Comparison of neutral density from AMPS & BATS-R-US

AMPS BATSRUS/SWMF

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

COMETARY NEUTRAL AND PLASMA ENVIRONMENT SIMULATIONS WITH RMOC

SHAPE MODEL

Comparison of bulk velocity from AMPS & BATS-R-US

AMPS BATSRUS/SWMF

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

COMETARY NEUTRAL AND PLASMA ENVIRONMENT SIMULATIONS WITH RMOC

SHAPE MODEL

Comparison of neutral density from the simulation and COPS

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

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.

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

COMETARY NEUTRAL AND PLASMA ENVIRONMENT SIMULATIONS WITH RMOC

SHAPE MODEL

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

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.