l. desorgher, m. gurtner, and e.o. flückiger...
TRANSCRIPT
PLANETOCOSMICS
L. Desorgher, M. Gurtner, and E.O. Flückiger Physikalisches Institut, University of Bern
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
OverviewPresentation of the projectSpace coordinate convertor Magnetic fieldAtmosphere modelSoil modelSome simulations results
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
GEANT4C++ toolkit for Monte Carlo simulation of hadronic and electromagnetic interaction of particle/radiation with matterPropagation in B field and E field can be taken into accountField of applications:
● Detector design and calibration● Medical applications● Space applications
==> Interaction of space radiations with planet
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Magnetocosmics Geant4 ApplicationPropagation of cosmics rays in the Earth's MagnetosphereVisualisation and cutoff rigidity computation
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
ATMOCOSMICS Geant4 ApplicationPropagation of cosmics rays in the Earth's Atmosphere
Secondary fluxes in atmosphere
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Presentation of the project MAGNETOCOSMICS and ATMOCOSMICS•Propagation of cosmic rays in the Earth's magnetosphere and atmosphere
Aim of this project•Extension of these codes to other planet with
Mars and Mercury as first case•Magnetosphere, atmosphere, soil models
=> PLANETOCOSMICS
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
PLANETOCOSMICS Simulate the electromagnetic and hadronic interaction of space radiations with planet atmosphere and soil
Compute the propagation of charged particles in planetary magnetic field
Developed for Earth, Mars and Mercury but can be extend to other planets quite easily (for C++ lover)
Computation of :magnetic shieldingenergy deposited in atmosphere> ionisation rateflux of particles at user defined altitude and/or depths
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Work Packages WP1•General space coordinate convertor for planets
WP2•General planetary magnetic field models• Implementation of Mars Crustal magnetic field
WP3•General atmospheric model•Mars atmosphere •Soil model •Development of the code for Earth, Mars, and Mercury
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Space coordinate convertor•Extension of Earth space coordinate to other planets– Geographic (GEO) > Planetocentric (PLA) – GEODETIC>Planetographic (PLAG)– GSE>PSO, PSE, PSEQ– If global magnetic field • MAG>PMAG, GSM>PSM, SM>PSMAG
• Information needed– SunPlanet direction in HAE2000– Sun and planet orientation in GEI2000– Prime meridian in GEI2000– Transformation from GEI2000 to HAE2000 – Global dipole momentum in PLA
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Space coordinate convertor
Orbit and orientation of the planet computed:By using of the Spice library By using Keplerian theory
Fränz and Harper, Plan. Space Sci., 2002Simon et al. A&A, 282,663,1994
Development of a SpaceCoordinatePlanet classEarth, Mars, MercuryEasy to extend to other planets
Test of Space coordinate convertor
Time (hour)
Pos
itio
n R
elat
ive
dif
fere
nce
PSOPSEQ
Spice
Kepler theory
Mariner10 Mercury flyby Spacecraft position provided in PLA, PSO and PSEQ PSO and PSEQ positions recomputed with the Space coordinate convertor from PLA position
Magnetic Field
Common to all planets•Dipole, Spherical Harmonic•Constant field•Orientation for flat geometry•Flat grid model Specific to planets •Earth=> IGRF, Tsyganenko•Mars=> Crustal models•Mercury=> Dipole
Bfield orientation for Flat geometry
Planetary coordinate system (X',Y',Z')Local coordinate system (X,Y,Z)Center of the simulation box C defined by the user in (X',Y'Z')B computed in (X',Y',Z') and transformed(X,Y,Z)
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Grid Model for flat geometryDivision of the world box in a uniform cartesian grid with (nx, ny,nz) cellsComputation and copy of the magnetic fields at the different nodes of the gridBfield at a given position is computed by linear interpolation of the Bfield at the nodesMuch faster
=> May be implementation in Spherical Geometry
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Field lines Flat GRID /Cain50
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Crustal Magnetic field of MarsMars Global Surveyor (MGS):
● Aerobraking orbits (alt >101.6km)● Science phasing orbits (alt >170. km)● Mapping orbit (alt ~400 km)
MGS Magnetic field measurement : ● No global field (dipole at equator <0.5 nT) ● Strong crustal field in the southern high lands :
1600 nT at 100 km over some regions 10x higher than on Earth Signature of an old global magnetic field
● Interaction of the solar wind with Mars ionosphere and crustal field
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
MGS observation Br @ 400 km
Connerney et al., Geophys.Res.Let. 28, 21, 40154018, 2001
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Connerney et al., Geophys.Res.Let. 28, 21, 40154018, 2001
Br vs geology
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
•Crustal magnetization seems to follow the topographical dichotomy of Mars:– low lands B weak, high lands B strong– north lands were probably formed after the cessation
of the Mars dynamo•Eastwest band of inverse polarity in high lands at ~180 lon:– possible signature of early sea floor spreading – change of the polarity of Mars global field in the past
•No magnetization over large impact basins of Hellas and Argyre:– Large impact did remove the crustal field in these
regions
MGS observation Interpretation
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Mars Crustal field modelsPurucker et al., Geophys. Res. Let. 27, 16, 2449, 2000:
11550 Radial dipole distributed all over the surface of MarsDipole moment computed to best fit the MGS radial field data @ <200km
Developed to produce magnetic field map at 200 km for geological study
Available and implemented in PLANETOCOSMICS
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Mars Crustal field models
ArkaniHamed, J. Geophys. Res. 106, E10, 23197, 2001:50 degree spherical harmonic modelModel coefficient computed to best fit the MGS data @ <200kmDeveloped to produce magnetic field map at 120 km Not available
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Mars Crustal field models
Cain et al., J. Geophys. Res. 108, E2, 5008, 2003:90 and 50 degree spherical harmonic model90 degree model developed to bestfit all MGS data50 degree model developed to best fit the MGS mapping orbit data (~400 km)The 90 degree model is needed to match the smaller scale structureProbably the best one Available and implemented in PLANETOCOSMICS
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Field lines Cain50 (spherical geometry)
PlanetAtmosphereCommon to all planets•Attribute vectors defining p, n, T, & composition vs altitude
•Definition of atmosphere structure by an ASCII table
•Specific to a planet• Interface with a model for defining the p, n,... vectors
•Earth Model : NRMLSISE00, MSISE90
•MarsModel : MarsGRAM2001
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
NASA MarsGRAM2001 model
•p,n, T in function of :• Lat., long. (topography from MOLA)• Altitude, season, local time, F10.7• Dust models
•Based on :• Nasa MGCM 080 km• Univ. of Arizona MTGCM 80170 km
• Implementation in PLANETOCOSMICS:Python script that convert MarsGram2001 output into a PLANETOCOSMICS atmospheric table
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Soil model
Different layers For each layer definition of
DensityComposition (50% SiO2, 25%...., ) Thickness
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Cutoff Rigidities vs position
Rc [G
V]
Magnetic shielding on Earth
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Altitude [km]
Ion
s p
air
pro
du
ctio
n r
ate
#/cm
3/s
Cosmic ray shower flux in Earth's atmosphere
Om
nid
irec
tion
al f
lux
[cm
2s1
]
Depth [g/cm2]
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
5MeV electrons in the region of Mars with the strongest crustal field
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Magnetic shielding on Mars at 47.8 N and 174 E
10 MeV e 1 MeV e
Tracking of 107 downward monoenergetic particles starting at 300 km altitude and distributed uniformly over a 1200 km *1200 km wide areaDetection of nb of particles that hits the ground in function of position
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Magnetic shielding on Mars at 47.8 N and 174 E
10 MeV proton 100 keV proton
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Computation of radiation flux on Mars
Simulation of the interaction of galactic cosmic ray proton with the Martian soil and atmosphere at 47.8 North, 174 E
Computation of resulting radiation at surface level andand in the atmosphere
Atmosphere 13,3 g/cm2 thick 95,7 %CO2 , 2.7% N2, 1,6 % Ar
Soil
density 3.5 g/cm3
compositon as measured by the alphaproton X ray spectrometer
on PathfinderSojourner (Boyce 2002)
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Flux of e and protons on Mars surface induced by galactic cosmic ray protons
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Flux of gamma induced by galactic cosmic ray protons during solar minimum
PLANETOCOSMICS 14 September 2004 Progress meeting Estec
Flux of neutrons on Mars induced by galactic cosmic ray protons at solar minimum
10 GeV protons e >1 MeVe+ > 1 MeVproton > 10 MeV
Mercury Soil + Dipole B0= 300 nT
Mercury Soil + Dipole B0= 300 nT
10 GeV protons from daysidee >1 MeVe+ > 1 MeVproton > 10 MeV
Quasi trapped e in Mercury dipole field
Quasi trapped e+ in Mercury dipole field
Quasi trapped protons in Mercury dipole field
10 GeV protons neutronsgammas
Possible future work
Take into account the convection and induced electric fieldImplement a more accurate magnetosphere model for MercuryAdd Jupiter case (study of magnetic shielding and CRAND)Modelise sputtering processTake into account the gravitation field...
For more informations
Email to [email protected]