Table of Contents ECSS Model Page
Background Information Geant4 tools
Planetocosmics

Table of contents

  1. Overview of Planetocosmics
  2. Planetocosmics in the SPENVIS environment
  3. Source
  4. Planetary settings
    1. Magnetic field
    2. Atmosphere
    3. Soil
  5. Geometry
  6. Analysis parameters
    1. Particle fluxes
    2. Energy deposition
  7. Material definition
  8. Stopping conditions
  9. Results
  10. References

Overview of Planetocosmics

The Planetocosmics application allows the definition of a planetary magnetic field, atmosphere and soil (currently only Mercury, Earth and Mars are implemented) and is using the Geant4 toolkit to simulate the hadronic and electromagnetic interactions of cosmic rays with the planetary environment.

These simulations can be highly time-consuming. Thus, since the CPU time available on SPENVIS for a single user is limited, the calculations are stopped if the program duration time exceeds a limit. This can be often the case for calculations on maps or orbit trajectories. Therefore, users are welcome to utilize SPENVIS to produce and download the macro-file but is recommended that they download the stand-alone version of Planetocosmics to make a run.

Note that the Planetocosmics application makes use of the Geant4 toolkit [4]. The complete Planetocosmics user manual is available online as a PDF-document.

Planetocosmics in the SPENVIS environment

The SPENVIS interface to Planetocosmics simplifies the process of defining run parameters via a number of input pages (see below) that a user can access from a table on the main page of the model. In addition, some information on the status and a short summary of the user input is also displayed.

Users can go to any particular input page and enter their settings. After they are done, they can hit the button and return to the main model page. Once they are satisfied with all their input they can use the button to generate the macro file. Pressing the button will start the calculation and bring up the results page.

Advanced users have the option to input a number of fine-tuning parameters.

Since the model uses a Monte-Carlo simulation-based code, execution times can be very long, certainly for cut-off calculations. The execution is limited to five minutes of CPU-time on the simulation machine. If the Planetocosmics run exceeds this limit, the simulation will be terminated and intermediate results returned to the user.

Source particles

Users can specify the incident particle, its energy spectrum and angular distribution using the “source particles” template that is common for the Geant4 tools in SPENVIS.

Planetary settings

A user can provide input, when applicable, defining the magnetic field, atmosphere and soil of the a particular planet (currently only Mercury, Earth and Mars are considered).

Magnetic field:

Mercury:

The internal magnetic field is assumed to be a non tilted centered dipole with B0=300 nT. There is no external magnetic field.

Earth:

The geomagnetic field can be defined in terms of an internal and external magnetic field. A user must also specify the reference date in terms of universal time. Depending on the choice of the magnetic field model, additional parameters can be added
Only advanced users have the option to select the Tsyganenko 96 or the Tsyganenko 2001 external magnetic field options.

Mars:

Mars lacks a global magnetic field. Nevertheless, some of its regions possess a crustal magnetic field. Its effect can be taken into consideration by selecting one of the three crustal magnetic field models available for Mars: .

Atmosphere

When an atmospheric model is selected a user can also specify the height above the atmosphere. Otherwise, the height above the surface of the planet can be given as an input.

Mercury:

No atmospheric model available for Mercury (planet has no atmosphere).

Earth:

There are two atmospheric models available for Earth, the MSISE90 and NRLMSISE00. There is also a number of parameters that a user can specify after a selecting an atmospheric model. These include a reference longitude and lattitude in [degree], the solar flux parameters F10.7 (previous day) and F10.7 (81 day average) in [10-22W m-2 Hz-1] and a daily Ap geomagnetic index parameter in [2nT]. Finally, these atmospheric models require also a reference date. It is assumed to be the same date as the one defined for the geomagnetic field (see above).

Mars:

The martian atmosphere is taken into consideration in terms of an engineering atmospheric model called Mars-GRAM 2001. The model is based on input data tables and a user can choose , depending on the position on Mars.

Soil

All three planets share the same options for the definition of the soil: . When the soil is defined in terms of soil layers (up to three layers), a user can specify the composition (material) and the thickness (measured in ) of the layer. A link to the material definition tool is also available via the edit materials button.

Mercury:

The default soil for Mercury is assumed to be a 10 m thick layer with 1.3 [g/cm3] density. The composition of this layer is shown in the following table:

  Material     SiO2     MgO     Al2O3     CaO     FeO     Na2O     TiO2  
  Abundance [%]    45   35     7     7     5     0.7     0.3

Earth:

The default soil for Earth refers to a 10 m thick layer of SiO2 (1.7 [g/cm3]).

Mars:

The Mars default soil is modeled by a 10 m thick layer with 1.7 [g/cm3] density with the following composition:

  Material     Na2O     MgO     Al2O3     SiO2     SO3     K3O     CaO     TiO2     Fe2O3  
  Abundance [%]      1.5     7.7     8.1   46.8     6     0.2     6.2     1.1   18.8

Geometry

There are two types of geometries available in Planetocosmics:

When flat type geometry is selected, the inputs for the reference coordinate system, longitude and latitude are used for specifying the centre of the Planetocosmics simulation world. Then, the initial position of the source is defined by the two Cartesian coordinates X, Y and the altitude (all three measured in [km] or planet’s radius, [Rp]) provided by the user.

However, for the spherical geometry is sufficient to provide only a longitude, latitude and altitude (the two first in degree and the latter in km or planet’s radius) and the reference coordinate system.

The possible potitional reference coordinate systems are:

For both types of geometry the user can specify the initial direction of the source by providing a zenith and azimuth angle (both in degree) measured in one of the following coordinate systems:

Note that the SPENVIS background pages contain a detailed description of all the coordinate systems used in Planetocosmics for Earth. The coordinate systems for the other planets can be defined in a similar way.

Analysis parameters

There are two possible types of analysis available in the SPENVIS implementation of Planetocosmics: particle fluxes or energy deposition.

Particle fluxes

Planetocosmics can register the flux of primary and secondary particles as a function of kinetic energy. The user can provide the number of energy bins dividing the energy axis and the binning mode:

A user can specify the energy range by providing a minimum and a maximum energy value in .

In a addition, one can choose one or more secondary partcle types to be considered in the analysis from the following list:

Finally, a user can define up to 5 detectors by providing the detector's altitude in [m] or [km]. Note that these detectors indicate the altitudes where flux of shower particles will be registered during the Planetocosmics simulation.

Energy deposition

Planetocosmics can calculate the energy deposited by incident particles in the atmosphere as a function of altitude and atmospheric depth. In addition, energy deposition in soil is also calculated as a function of soil thickness and depth.

The user can provide the number of bins dividing the altitude/depth axis for the atmosphere and the depth/thickness axis for the soil.

Material definition

Users can employ the “material definition tool” to either specify their own material or make use of the predefined lists.

Stopping conditions

In order to limit the computing time during a Geant4 simulation secondary electrons, protons and gamma are tracked only if their range in the material where they are produced is higher than the cut in range parameter.

When an atmospheric model is selected, a user has the possibility to provide a cut in range that is constant in depth (but not in length) for the whole atmosphere. This in turn prevents the production of the selected particles below an energy threshold. A user can also select a cut in range for a given soil layer. In both case the cut in range is measured in .

Results

Planetocosmics produces the files listed in the table below. A description of the format of the files can be brought up by clicking on their description in the table.

The macro file spenvis_pco.g4mac contains the Geant4 Macro file. The log file spenvis_pco.g4log records the output from Planetocosmics to stdout and stderr. The output file spenvis_pco.txt contains tabulated results according to the selected analysis scenario (particle fluxes or energy deposition).

Output files generated by Planetocosmics
File name Description
spenvis_pco.g4mac Geant4 macro file
spenvis_pco.g4log Log file
spenvis_pco.txt Outputs for the various analysis type

To generate plots, select the plot type(s), options and graphics format when applicable, and click the button. The current page will be updated with the newly generated plot files.

References

  1. Cain, J.C., B. B. Ferguson, and D. Mozzoni, An n=90 internal potential function of the Martian crustzal magnetic field, J. Geophys. Res., 108, E2, 5008, 2003
  2. Connerney, J. E. P., M. H. Acuna, P. Wasilewski and G. Kletetschka, The global magnetic field of Mars and implications for crustal evolution, Geophys. Res. Let., 28, 4015-4018, 2001
  3. Cooke, D. J., J. E. Humble, M. A. Shea, D. F. Smart, N. Lund, I. L. Rasmussen, B. Byrnak, P. Goret, and N. Petrou, On cosmic-ray cutoff terminology, Il Nuovo Cimento, 14C, 213-234, 1991.
  4. Geant4
  5. Hapgood, M. A., Space Physics Coordinate Transformations: a user guide, Planet. Space Sci., 40, No 5, 711-717, 1992.
  6. Hedin, A. E., Extension of the MSIS thermosphere model into the middle and lower atmosphere, J. Geophys. Res., 96, A2, p. 1159-1172, 1991.
  7. IGRF model of the International Association of Geomagnetism and Aeronomy (IAGA)
  8. Langel, R. A., Main field in geomagnetism, Vol I, ed. J. A. Jacobs, Academic Press, London, 249-512, 1987.
  9. Mars-GRAM 2001
  10. Miroshnichenko, L., Radiation Hazard in Space, Astrophysics and Space Science Library, Vol 297, Kluwer Academic Publishers, Dordrecht, 2003.
  11. Picone J. M., A. E. Hedin, D. P. Drob, and A. C. Aikin, NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues, J. Geophys. Res., 107, A12, 1468, 2002.
  12. Press W. H., S. A. Teukolsky, B. P. Flannery, and W. T. Vetterling, Runge-Kutta method, in 'Numerical Recipes in C++, The art of scientific computing, 2nd ed., Cambridge University Press, p 715, 2001.
  13. Purucker M., D. Ravat, H. Frey, C. Voorhies, M. Acuna , An altitude-normalized magnetic map of Mars and its interpretation, Geophys. Res. Let, 27,2449-2452, 2000
  14. Russell, C. T., Geophysical Coordinate Transformations, Cosmic Electrodyn., 2, 184, 1971.
  15. Tsyganenko, N. A., Global quantitative models of the geomagnetic field in the cislunar magnetosphere for different disturbance levels, Planet. Space Sci., 35, 1347, 1987.
  16. Tsyganenko, N. A., A magnetospheric magnetic field model with a warped tail current sheet, Plant. Space Sci., 37, 5, 1989.
  17. Tsyganenko, N. A., Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause, JGR, 100, 5599, 1995.
  18. Tsyganenko, N. A., Effects of the solar wind conditions on the global magnetospheric configuration as deduced from data-based field models, Eur. Sace Agency Spec. Publ., ESA SP-389, 181, 1996.
  19. Tsyganenko, N. A., A model of the near magnetosphere with a dawn-dusk asymmetry, 1. Mathematical structure, JGR, 107, No A8, 10.1029/2001JA000219.
  20. Tsyganenko, N. A., A model or the near magnetosphere with a dawn-dusk asymmetry, 2. Parameterization and fitting to observations, JGR, 107, N0 A8, 10.1029/2001JA000220.
  21. Wolf, R. A., Magnetospheric configuration, in 'Introduction to space physics', ed. M. G. Kivelson and C. T. Russell, Cambridge University Press, 288-329, 1995.


Last update: Wed, 23 Mar 2016