Abstract
Data assimilation schemes with empirical background models of the
ionosphere are already in operational use. However such methods suffer
during disturbed conditions when large gradients are present and are
moving relatively fast through the modeled domain. Also, such schemes
have limited forecasting capabilities. In order to improve disturbed
conditions modeling, more sophisticated assimilation schemes based on
sparse measurements for the coupled thermosphere ionosphere system are
needed. We have implemented an ensemble Kalman Filter (enKF) for the
Thermosphere-Ionosphere (TI) system. We used the Coupled Thermosphere
Ionosphere Plasmasphere electrodynamics (CTIPe) model as the background
for an assimilation scheme and created the Thermosphere Ionosphere Data
Assimilation (TIDA) software package. We published our first paper
discussing neutral mass density assimilation during quiet geomagnetic
conditions in Space Weather in 2018. In this paper we present results
from experiments during the 2003 Halloween Storm, 27-31 October 2003,
under very disturbed (K$_p$ = 9) conditions while assimilating
GRACE-A and B, and CHAMP neutral density measurements. TIDA was able to
simulate this disturbed period without using the L1 solar wind
measurements which were contaminated by solar energetic protons, by
estimating the model inputs from the density measurements. TIDA is being
prepared to offer specification and short term forecasts of neutral
density for satellite drag and debris collision avoidance for space
traffic management. We also plan to offer long term (solar cycle
length), average neutral density estimation for satellite fleet
management.