Modelling The TARANIS XGRE Insturment For Terrestrial Gamma Ray Flashes and Associated Electron Beams

Abstract:

The IDEE and XGRE instruments on-board the TARANIS satellite are key experiences of the mission with ambitious scientific objectives concerning Terrestrial Gamma Ray flashes (TGFs), associated electron beams (TEBs), and couplings between the atmosphere and the radiation belts. At the altitude of the satellite, the instruments will measure X and gamma rays produced from sources at lower altitude, and filtered by the atmosphere, together with secondary produced relativistic electrons and positrons. Such measurements only give an indirect access to the source of the TGF, and we need a numerical model of the transport of these burst emissions through the atmosphere, and their interactions with the satellite, including the response of the detectors. This theoretical-experimental approach provides a way to relate the source region to the observations which will be used to better constrain the TGF production mechanism.

A first stage has already been accomplished by developing the MC-PEPTITA Monte Carlo model (see Sarria et al. 2015, JGRA) which is able to model the transport of X/gamma-rays and relativistic electrons/positrons through the atmosphere, from the source region up to the altitude of the satellite. The next step is to extend this model to take into account the detection of the energetic particles by the three XGRE sensors by making a full GEANT4 model, validating it by comparison with laboratory experiments, and building its response matrix (for photons and electrons). In this presentation, we will present this strategy in detail, and discuss some preliminary results.