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Computer Simulations in Solar System Physics
Mats HolmströmSwedish Institute of Space Physics (IRF)
Forskarskolan i rymdteknikGöteborg
12 September 2005
Solar System Physics and Space TechnologySSPT
Scientific Goals
● How does the interplanetary medium affect and shape the bodies in the inner solar system?
● What plasma physical processes determine the structure of the interaction regions?
● How do the solar system dust population evolve and interact with planetary bodies?
Study the environment and the solar wind interaction as well asthe evolution and dynamics of solar system objects with focus on the inner planets, moons, asteroids, comets and dust. Development of scientific instrumentation for satellite-based measurements in support of space exploration.
Overview
● The science we do● The simulations we do. Some examples:
1. Ion precipitation at Mercury
2. Instrument design
3. Energetic neutral atom (ENA) production at Mars
4. ENA production at the Moon
5. Solar wind charge exchange X-rays at Mars
6. Magnetohydrodynamics and particle simulations
Solar Wind-Solar System Objects Interaction
[Kivelson and Russel]
Detectors of ...
● ... Ions, and● ... Energetic Neutral Atoms (ENAs)
Direction, flux, mass, energy/velocity
Current and Future Missions
Simulation Needs
1) Proposals and Mission planning
• What is the sensor environment?• What can we detect? What science can be done?• Example: Sputtered neutral atoms at Mercury
2) Instrument design
• Optimization (performance-weight-power)• Example: Neutral atom detector for Mercury and the moon
3) Data analysis
• Extract as much information as possible• Example: ENA production at Mars
Ion Trajectories
Example 1: Sputtered neutral atoms at Mercury
Ion Precipitation Map
Example 1: Sputtered neutral atoms at Mercury
The three columns correspond to, from left to right, sputtering fromsolar wind protons, from magnetotail accelerated protons, and fromsodium photoions. The top row show maps of the ion precipitation on Mercury's surface[1/(cm^2 s)]. The subsolar point has zero longitude and latitude. The bottom row shows the fluxes of sputtered sodium atoms in theenergy range 10-40 eV as seen from a height of 400 km over areas of large precipitation with a 160 degree field of view. The unit is [1/(cm^2 sr s)
Example 1: Sputtered neutral atoms at Mercury
Simulation Details
● C++● RKSUITE for the trajectory
computationAdaptive Runge-Kutta ODE solver
● Parallelize the trajectory computations
● MPI for communication
Example 1: Sputtered neutral atoms at Mercury
Designing a Neutral Atom Imager
● For missions to the moon and to Mercury● Particle trajectories in the sensor by an MPI
application (A. Fedorov, CESR, France)● Optimize weight (dimensions) and mass resolution
Example 2: Neutral atom detector for Mercury and moon
Electric Potential
Example 2: Neutral atom detector for Mercury and moon
Particle Trajectories
Example 2: Neutral atom detector for Mercury and moon
Mass Resolution
Example 2: Neutral atom detector for Mercury and moon
ENA Production at Mars
● Generated by – Solar wind-exosphere charge exchange– Atmospheric sputtering and backscatter
(of precipitating ions and ENAs)– Planetary ions-exosphere charge exchange– Solar wind-Phobos gas torus charge exchange
● Three-dimensional emissions
Example 3: ENA Production at Mars
[Futaana, 2004]
ENA imager Field of View at Mars
Example 3: ENA Production at Mars
Different ENA production models
Empirical Hybrid MHD
Sensitive to Flow model Exosphere model
Example 3: ENA Production at MarsEffects of parameter changes
Interpreting ENA images at Mars
ENA flux = Line of sight integration (ion flux and neutral density)
Inverse problem(forward modeling)
Example 3: ENA Production at Mars
ENA Production at the moon Generated by sputtering from
Micro meteoroid impact vaporization Photon desorption Precipitating
Magnetospheric ions Solar wind ions
Significant contribution only from precipitating solar wind ions
Two-dimensional emissions
Example 4: ENA Production at the Moon
[Futaana, 2004]
Example 4: ENA Production at the Moon
What can we learn from moon ENA images?
● Regolith composition● Size and location of magnetic anomalies● Space weathering effects on the regolith
Solar wind flow around an anomaly[Harnett and Winglee]
[Futaana, 2004]
Example 4: ENA Production at the Moon
ENA imaging of shaded areas
● Kinetic effects => solar wind ion precipitation in shaded areas
[Clementine]
Example 4: ENA Production at the Moon
Solar Wind Charge Exchange X-rays
Observation Simulations
Example 5: SWCX X-rays at Mars
The FLASH Code● Magnetohydrodynamic (MHD) solver that can include particles
● From University of Chicago
● General compressible flow solver
● Adaptive (Paramesh) and parallel (MPI)
● Open source, Fortran 90
● Add boundary conditions and sources for solar system objects - solar wind simulations(Mercury, Venus, earth, moon, Mars, ...)
● First investigations:
– A comet (MHD with a photoion source)
– Mars' exosphere (particles)
Example 6: Magnetohydrodynamics and particle simulations
Simulations is an integral part of our science