Validation of Model Results in Response to the COSPAR ISWAT Challenge

The COSPAR International Space Weather Action Team (ISWAT) facilitates global
collaboration to address challenges across the field of space weather. The G3-04 team, “Internal
Charging Effects and the Relevant Space Environment”, aims to systematically assess and
improve model performance under different conditions. In response to the team's first bench-
marking challenge (long-term simulation), this study validates the Versatile Electron Radiation
Belt (VERB) code by performing simulations for the entire year of 2017 and validating the
simulation results against observations from NASA’s Van Allen Probes. No measurements from
Van Allen Probes are used in the model setups, including both initial and boundary conditions.
The only data input employed in our simulations is obtained from the Geostationary
Operational Environmental Satellites (GOES) to define the outer boundary condition. Then,
the validation is conducted by comparing simulated differential electron fluxes at 0.9 MeV and
57.27 degrees pitch angle with observations from the Van Allen Probes. Overall, our simulation
results show good agreement with observations. Model performance is evaluated by calculating
several different metrics such as root mean square error, prediction efficiency, median
symmetric accuracy, and normalized difference. Similar approach is extended to multi-year
simulations, validated against satellite data for both long-term trends and specific geomagnetic
storm events, providing a comprehensive assessment of model accuracy.