BAS_RBM

The BAS Radiation Belt Model (BAS-RBM) is described in Glauert et al. (2014 a, b). The BAS model simulates changes in the high-energy electron population of the radiation belts taking into account effects such as the changing solar activity and wave-particle interactions. The BAS-RBM is a three-dimensional, time-dependent diffusion model for phase-space density based on solution of the Fokker-Planck equation. This will help to improve our understanding of the processes involved and help us develop warning and forecasting capabilities.

The BAS model is currently being developed to provide now-casts for the radiation belts as part of the SPACECAST Framework-7 project and to understand the radiation belts at Jupiter and Saturn.

The model is very configurable, but for these results, it has been configured in a similar way to that used for forecasting (Glauert et al., 2021).

Coordinate System: The model uses 2 coordinate systems to construct computational grids:(L*, α, E) and (L*, μ, J).

Numerical method: Implicit finite difference scheme.

0o ≤ pitch-angle ≤ 90o The energy and L-shell grids can be varied but typically 1 ≤ L≤ 7 and 10 MeV/G ≤ μ ≤ 2000 MeV/G at L = 6.5

The input data for the simulation are just the GOES 15 >800 keV electron flux, the KP and AE indices and solar wind data for the period.

Radial diffusion is modelled using the Brautigam and Albert (2000) electromagnetic radial diffusion coefficient. Waves included in the simulation are: Plasmaspheric hiss and lightning-generated whistlers (Glauert et al., 2014) Upper and lower band chorus waves (Reidy et al., 2021) EMIC waves (Ross et al., 2020) Magnetosonic waves (Wong et al., 2022) Collisions with the atmosphere are modelled following Abel and Thorne (1999) The outer radial boundary is set at L*=6.1. The boundary condition is derived using the technique described in Glauert et al., 2018, but it has been applied to the >800 keV flux, rather than the >2 MeV flux. The low energy boundary is set at 100 keV at L*=6.1 and is derived using the same method as Glauert et al., 2018. The inner radial boundary is set at L*=2 and the boundary condition is derived using the same method as used in Glauert et al. (2018). The simulation was started on XX December, using a precomputed steady state as the initial condition. The results from before the 1st of January 2017, when the model was adapting to the conditions at the time, are not given.

The model produces a time-series of the flux or phase-space density on the 3-d grid

Two files are provided, one each for VAP-A and VAP-B. The VAP-A file is called ‘2017_BAS-RBM_VAP-A.dat’, and the one for VAP-B is named similarly. These files are self-explanatory ASCII files with a short header, followed by lines with the format: Date, time, 900keV VAP flux, 900 keV model flux, 1.7 MeV VAP flux, 1.7 MeV VAP flux The fluxes are at a local pitch-angle of 57.27 degrees. When the spacecraft is outside the simulation region, or the L* of the spacecraft is not provided, then the model flux may be shown as NaN.