Energetic Particle Radiation Environment Module (EPREM)
It is a parallelized energetic particle transport and acceleration numerical kinetic code, solving for energetic charged particle distribution change along and
across magnetic field lines in 3-dimensions. The code can easily be modified to work in energies regimes from Kev to Gev and to treat different energetic particle
spicies. The boundaries of the EPREM model, the spatial resolution can all be altered by modifying the configuration files. The code will produce the time histories of
the particles distribution functions at various pitch angles, energies and locations in the heliosphere. The code is written in the C.
The EPREM Grids
The grid assumes thr 3-D interplanetary magnetic field, along which energetic particles propagate. The spatial grid is housed in adata structure based on nested cubes,
whose surfaces are subdivided into arrays of cells. The cubes have 6 faces, r rows and c columns on their surface. Each cell defines a grid node at its center. Every node
has inward and outward neighbors, which are nodes that hold the same face, column and row index on the proceding and following shells. Each node carries information about
its position in 3D, as well as the information about the local solar wind conditions, and the distribution function values at its instantaneous location.
A new cube shell of nodes is created at the fixed inner boundary, its nodes’ positions are normalized to the spherical surface of the inner boundary. Shell data move outward
from cube to cube. The cube structure is static, while the shell nodes stream through it.
EPREM uses the MPI to enable to be excuted on multiply processors. Every processor receives a certain number of cube shells on which it performs the computations.
For each processor, its inner-most cube shell serves as a communications buffer to transfer information from the preceding processor.
(Schwdron et al ., 2010)
EPREM solves the 3-D particle focused transport equation which is given by (e.g. Skilling, 1971; Ruffolo, 1995):
In the grid of nodes, most of focused transport coefficients are obtained simply by differencing the state quantities at each node between the updated values
and the values at the previous time step.Since nodes lists are traced along field lines,the field line gradients are easily computed.