Table of Contents ECSS Model Page
Background Information Radiation sources and effects
Ion energy and LET spectra

Overview

Ion energy and LET spectra are calculated with models from the CREME model suite.

The input parameters and options for the model are described below. When the input form has been completed, pressing the button will start the calculation and bring up the "Results" page.

The button calls up the model selection page for consecutive runs of multiple models. This feature is available for advanced users only.

Warning: using these buttons deletes all existing output from the ion energy and LET spectra model and from any model that uses this output, in order to ensure consistency in the outputs.

Input parameters

The first parameter to be entered is the target material in which the LET spectrum is computed.

The second parameter to be entered is the spacecraft shielding thickness, in units of aluminium or aluminium equivalent thickness.

The cosmic ray and solar energetic particle environment contains ions of all elements. The composition is specified by means of a lower and upper limit for the elements to be considered in the calculation. The upper limit should be greater than or equal to the lower limit. The environment models currently implemented are those of CREME-86. For the galactic cosmic ray flux also the MSU model has been implemented in two versions: the standard model ISO-15390 and the model by R.A. Nymmik et al. (1996). The latter includes a rising flux at very low energies (around 10 MeV/nucleon).
The option "solar activity data" (only available when using the MSU model) allows the user to run the model for different epochs:
- Solar minimum (May 1996), corresponding to the epoch of solar minimum conditions
- mission epoch, corresponding to the epoch for which the orbit is generated
- user defined (only for the advanced user!)
By default tabulated solar cycle data (yearly sunspot numbers) from the year 1957 until 2007 are used. For future epochs the solar cycle is propagated by substracting 22*n years from the epoch. As an advanced user you can enter the solar cycle data. In this case one of the required user inputs is the sunspot number at (epoch - lag) where the lag is the delay time of the cosmic ray particle flux variations relative to the solar activity variations. We remark that (only) in this case the lag time is taken constant while it normally depends on the particle rigidity.

The particle environment outside the magnetosphere depends on the phase of the solar cycle and on flare activity. The phase of the solar cycle is derived from the orbit start date.

Cosmic ray and solar energetic particles are attenuated by the shielding effect of the Earth's magnetic field. Geomagnetic shielding is calculated for quiet or disturbed conditions of the magnetosphere, or can be ignored altogether, for instance to simulate interplanetary conditions.

SPENVIS Checks whether the trapped proton models have been run for the current project. If a spectrum file is found, and if the user has included protons in the environment composition, the trapped proton fluxes can be added to the solar and cosmic rays proton fluxes. The user also has the option to ignore the trapped proton fluxes.

SPENVIS calculates the geomagnetic transmission factors for each ion and for each energy at every orbital point. These factors are then integrated over the respective mission segments and folded with the interplanetary particle spectra. Advanced users have the option to select a higher output resolution, i.e. the creation of a supplementary output file containing full proton energy spectra and LET spectra at each orbital point (folded with the local geomagnetic cutoff function). This output file is then used in the single event upset rate calculation to produce a file with upset rates at every orbital point. The orbit averaged upset rates are not affected by the creation of the high resolution file.

Results

The ion energy and LET spectra model produces the files listed in the table below. A description of the file formats can be brought up by clicking on their description in the table.

The report file spenvis_lop.html contains the input parameters and summary tables. The spectrum file spenvis_lof.txt contains the proton and LET spectra averaged over each mission segment and the total mission averaged spectra. The optional spectrum file spenvis_loo.txt contains, for each orbital point, the full proton and LET spectra.

Output files generated by the ion energy and LET spectra model
File name Description
spenvis_lop.html Report file
spenvis_lof.txt Segment and mission averaged proton and ion spectra and LET spectra
spenvis_loo.txt Proton and LET spectra for each orbital point

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

The button calls up the output page for consecutive runs of multiple models. This button only appears when the ion energy and flux spectra model has been included in the combined model run selection. This feature is available for advanced users only.

References

Nymmik, R.A., Panasyuk, M.I. and Suslov, A.A., Galactic cosmic ray flux simulation and prediction: Adv. Space Res. Vol. 17, No. 2, 1996.

Last update: Mon, 12 Mar 2018