  We present our approach to modeling over 20 years of the solar
wind-magnetosphere-ionosphere system using version 5 of the Grand Unified
Magnetosphere-Ionosphere Coupling Simulation (GUMICS-5). As input we use 16-s
resolution magnetic field and 1-min plasma measurements by the Advanced
Composition Explorer (ACE) satellite from 1998 to 2020. The modeled interval is
divided into 28 h simulations, which include 4 h overlap. We use a maximum
magnetospheric resolution of 0.5 Earth radii (Re) up to about 15 Re from Earth
and decreasing resolution further away. In the ionosphere we use a maximum
resolution of approximately 100 km poleward of +-58 degrees magnetic latitude
and decreasing resolution towards the equator. With respect to the previous
version GUMICS-4, we have parallelized the magnetosphere of GUMICS-5 using the
Message Passing Interface and have made several improvements which have e.g.
decreased its numerical diffusion.
  We compare the simulation results to several empirical models and geomagnetic
indices derived from ground magnetic field measurements. GUMICS-5 reproduces
observed solar cycle trends in magnetopause stand-off distance and
magnetospheric lobe field strength but consistency in plasma sheet pressure and
ionospheric cross-polar cap potential is lower. Comparisons with geomagnetic
indices show better results for Kp index than for AE index. The simulation
results are available at
https://doi.org/10.23729/ca1da110-2d4e-45c4-8876-57210fbb0b0d, consisting of
full ionospheric files and size-optimized magnetospheric files. The data used
for Figures is available at https://doi.org/10.5281/zenodo.6641258.
  Our extensive results can serve e.g. as a foundation for a combined
physics-based and black-box approach to real-time prediction of near-Earth
space, or as input to other physics-based models of the inner magnetosphere,
upper and middle atmosphere, etc.

Space Physics