L. Desorgher, M. Gurtner, and E.O. Flückiger ...cosray.unibe.ch/~laurent/...finalpres_15112004.pdf · PLANETOCOSMICS 14 September 2004 Progress meeting Estec Space coordinate convertor

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


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


Magnetocosmics Geant4 ApplicationPropagation of cosmics rays in the Earth's MagnetosphereVisualisation and cutoff rigidity computation


ATMOCOSMICS Geant4 ApplicationPropagation of cosmics rays in the Earth's Atmosphere

Secondary fluxes in atmosphere


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 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


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


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


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)


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


Field lines Flat GRID /Cain50


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


MGS observation Br @ 400 km

Connerney et al., Geophys.Res.Let. 28, 21, 40154018, 2001


Connerney et al., Geophys.Res.Let. 28, 21, 40154018, 2001

Br vs geology


•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


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


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


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


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


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


Soil model

Different layers For each layer definition of

DensityComposition (50% SiO2, 25%...., ) Thickness


Cutoff Rigidities vs position

Rc [G

V]

Magnetic shielding on Earth


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]


5MeV electrons in the region of Mars with the strongest crustal field


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


Magnetic shielding on Mars at 47.8 N and 174 E

10 MeV proton 100 keV proton


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)


Flux of e and protons on Mars surface induced by galactic cosmic ray protons


Flux of gamma induced by galactic cosmic ray protons during solar minimum


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]

Documents

L. Desorgher, M. Gurtner, and E.O. Flückiger ...cosray.unibe.ch/~laurent/...finalpres_15112004.pdf · PLANETOCOSMICS 14 September 2004 Progress meeting Estec Space coordinate convertor