Abstract
The EXospheric TEMeratures on a PoLyhedrAl gRid (EXTEMPLAR) method
predicts the neutral densities in the thermosphere. The performance of
this model has been evaluated through a comparison with the Air Force
High Accuracy Satellite Drag Model (HASDM). The Space Environment
Technologies (SET) HASDM database that was used for this test spans the
20 years 2000 through 2019, containing densities at 3 hour time
intervals at 25 km altitude steps, and a spatial resolution of 10
degrees latitude by 15 degrees longitude. The upgraded EXTEMPLAR that
was tested uses the newer Naval Research Laboratory MSIS 2.0 model to
convert global exospheric temperature values to neutral density as a
function of altitude. The revision also incorporated time delays that
varied as a function of location, between the total Poynting flux in the
polar regions and the exospheric temperature response. The density
values from both models were integrated on spherical shells at altitudes
ranging from 200 to 800 km. These sums were compared as a function of
time. The results show an excellent agreement at temporal scales ranging
from hours to years. The EXTEMPLAR model performs best at altitudes of
400 km and above, where geomagnetic storms produce the largest relative
changes in neutral density. In addition to providing an effective method
to compare models that have very different spatial resolutions, the use
of density totals at various altitudes presents a useful illustration of
how the thermosphere behaves at different altitudes, on time scales
ranging from hours to complete solar cycles.