Validation of the Physical Model Salammbô-Protons with Van Allen Probes Data

Abstract:

The physical model Salammbô-3D is developed for about twenty years at ONERA and allows calculating electrons and protons flux in the Earth radiation belts. The Salammbô-3D models share a common architecture basis between the electron and the proton versions, as some physical processes acting in the Earth radiation belt are relevant for both species, such as magnetopause shadowing or more importantly, radial diffusion. This last process, modeled using magnetic field measurements at geostationary orbit (Lejosne et al., 2013), has been validated in both versions of Salammbô-3D and represents a rugged base of the code. Then several other physical processes exist and are linked with electrons only, as interaction with waves, or protons only, as charge exchange. Here, we will focus on the modeling of low-energy protons, from few tens of keV to about 1 MeV. For this energy range of protons two physical processes have been taken into account in Salammbô-3D: charge exchange and friction resulting from interaction with atmosphere. Several models of atmosphere are available and two of those will be investigate in this study: MSIS-86 (Hedin, 1987, 1991) and Hodges model (Hodges, 1994) Salammbô-3D results, using these two models will be compared to MAGEIS measurements for this energy range from Van Allen Probes data during a series of storms between February and May 2013. A comparison with CRRES/MEB measurements between August and October 1990 will also be done. The effect of each physical process will be studied. In particular, the major effect of charge exchange on the dynamics of protons with energy of few tens of keV will be highlighted and validated against Van Allen Probes data.