VERB-3D

The Versatile Electron Radiation Belt code (VERB) was developed by the Space Environment Modeling Group SEMG (http://rbm.epss.ucla.edu/) at the University of California, Los Angeles. The model has been described in Shprits et al., 2009, and Subbotin et al., 2010. It solves the Fokker-Planck equation for electron PSD [Schulz and Lanzerotti, 1974, Shprits et al., 2008b, Subbotin and Shprits, 2009]. The equation is solved using a finite differences approach and an implicit numerical scheme. The stability of such scheme is independent of the used time step. Following the approach used for the solution without mixed diffusion terms, described by Subbotin and Shprits[2009], the equation (1) is split into radial diffusion and local (energy, pitch angle, mixed) diffusion. The further separation of energy and pitch angle diffusion is impossible due to the existence of the mixed diffusion terms. Therefore, the implicit solution requires inversion of a model matrix of the 2-D operator on each time step. Inversion of such a big matrix is a quite time consuming computational operation, which is not required for the solution of the Fokker-Planck equation in the explicit formulation [Press et al., 1992]. However, the implicit scheme allows to use a longer model time step, while the time step in explicit scheme is limited by the Courant-Friedrichs-Lewy stability condition [Courant et al., 1928; Press et al., 1992], and the overall computational wall clock time with implicit scheme is lower.

The VERB code is written in C++, and was designed for use on a single-CPU computer and conforms to the C++ 2011 standard. The cross-platform code supports the compilation on various systems (Linux, Windows, Mac OS). Please see the link to the model description for more details

To improve the storm-based studies, the realistic field model will be included in the further model developments.

Inputs to VERB vary depending on the requested simulation. At a minimum, the user may just specify Kp and constant boundary conditions. GOES 13-15 measurements from the EPEAD (Energetic Proton, Electron and Alpha Detector) instruments may be used to scale the outer boundary in L-shell, which requires input of solar wind data in order to run the requested magnetic field model. These inputs are automatically generated for the requested model.

Outputs include the electron PSD (Phase Space Density) on the model grid, and optionally the invariant flux (electron flux computed from a dipole magnetic field model).

2016-08-04 Initial model installation 2016-09-08 Revision where model can run in separate instances 2016-10-27 Pre-calculated diffusion coefficient files available for reuse when the same grid is requested 2017-06-27 Use Matlab instead of Octave for interface scripts and plotting 2017-10-26 VERB code using OpenMP multi-threading