Help on away from 1 AU statistical modelling

Fluence and peak flux modelling away from 1 AU

In addition to various statistical models for fluence and peak flux at 1 AU, the SEPEM server also provides a tool for evaluating these quantities for a spacecraft mission away from 1 AU.

This tool is based on physical modelling of a number of reference event profiles (ten distinct sub-types) as a function of distance from the Sun, and fitting the resulting fluence and peak flux spectra to a distance scaling law. A subset of the SEPEM reference event list was classified in terms of the four event types found (divided in ten sub-types), resulting in a new event list to which the distance scaling relations can be applied. The event spectra at 1 AU were derived from the SEPEM reference proton dataset (RDS v2.1).The ten modelled events, the classification of events, and the derived dependence of the spectra with the heliocentric radial distance are described in the introduction to SOLPENCO2.

Event list selection

Given the specific nature of this application, there is no data table or response function selection option (as in the case for the models at 1 AU). Instead, the user can select a purpose built event list, as described above. Currently, only one such list is available, but more may be added in the future.

Model selection and parameters

This tool inherently uses the virtual timeline method, hence no analysis method selection is presented. Otherwise, the menu options and inputs are similar to the ones for the model at 1 AU, with two main differences:

There are no input fields for mission durations, as these are now generated by the tool from the mission profile (see next item).
In the mission time steps box, the user should enter a number (at least 2) of mission steps, each consisting of a time stamp and a helioradial distance in AU. Time stamps should be specified in the format YYYY-MM-DD hh:mm:ss. Distances can be entered in any float format, and should be separated from the time stamp by at least one blank character. A sample set of two input lines would look like
2015-07-13 15:03:00 1.32
2018-01-02 00:03:00 0.9
Dates before 1970 are not allowed. Mission steps should be entered in ascending order of time.

Model name and description

The user should specify a model name (which will be used as a label to identify the model run, for instance on the My SEPEM page) and a description for future reference. As the processing time for this tool can be several hours, it is run in batch mode, and the outputs will be stored after completion of the run, using the name and description entered prior to pressing the Run button. The model name cannot be left blank. If a model with the same name is already stored in the database by the current user, the model results will be over-written.

Once the run has been started, no other activity (except browsing the help pages) is possible on the server (with the current user account) until the run is completed. While the process is running, a page is presented where the user can perform a refresh to check for completion, or kill the running process. The user can log out and return to the server later.

Outputs

Overview

After completion of the model run, a new pane is shown with the model outputs. The outputs shown depend on the selected model parameters.

For comparison, the tool generates probability curves for three distance scaling laws:

no distance dependence: the fluence and flux at 1 AU is used;
the ECSS-E-ST-10-04C recipe: no scaling for distances >1 AU, and R^-2 scaling for distances <1 AU;
the SEPEM method using synthetic fluence and flux profiles.

At the top of the pane, links to two types of text files are provided:

event list: the start and stop times of the events within the epoch range of the selected data source, plus the time integrated and peak values for all data channels;
model files: the probability curves in text format.

Links to the waiting time distribution and departures (used for the solar maximum phases) are provided as well.

The table labelled Probability curves provides access to plots of the probability curves for each data channel, accumulated over the entire mission.

The table labelled Mission profile provides access to plots representing the evolution of the 90% confidence level values over successive solar cycle phases. Please note that these plots are only provided for reference: the total mission fluence and peak flux is not simply the sum or the maximum of the quantities shown in the plots.

As for the models at 1 AU, plots of the fluence or flux distribution functions (plus comparisons and departures) and of the duration fits (plus departures) are produced, for both solar maximum and solar minimum conditions. As the number of plots is large, they are not presented in a table, but can be extracted from the output zip archive (see below).

All output files (PNG plot files and text files) can be downloaded as a zip archive using the Supplementary outputs link: this will open a new window with a summary of the results and a link to the Zip archive of output files. All files are stored in the database and can be retrieved at any time from the My SEPEM page.

Last modified on: 13 April 2017.