  We investigate satellite orbital drag effects at low-Earth orbit (LEO)
associated with thermosphere heating during magnetic storms caused by coronal
mass ejections. CHAllenge Mini-satellite Payload (CHAMP) and Gravity Recovery
And Climate Experiment (GRACE) neutral density data are used to compute orbital
drag. Storm-to-quiet density comparisons are performed with background
densities obtained by the Jacchia-Bowman 2008 (JB2008) empirical model. Our
storms are grouped in different categories regarding their intensities as
indicated by minimum values of the SYM-H index. We then perform superposed
epoch analyses with storm main phase onset as zero epoch time. In general, we
find that orbital drag effects are larger for CHAMP (lower altitudes) in
comparison to GRACE (higher altitudes). Results show that storm-time drag
effects manifest first at high latitudes, but for extreme storms particularly
observed by GRACE stronger orbital drag effects occur during early main phase
at low/equatorial latitudes, probably due to heating propagation from high
latitudes. We find that storm-time orbital decay along the satellites' path
generally increases with storm intensity, being stronger and faster for the
most extreme events. For these events, orbital drag effects decrease faster
probably due to elevated cooling effects caused by nitric oxide, which
introduce modeled density uncertainties during storm recovery phase. Errors
associated with total orbit decay introduced by JB2008 are generally the
largest for the strongest storms, and increase during storm times, particular
during recovery phases. We discuss the implication of these uncertainties for
the prediction of collision between space objects at LEO during magnetic
storms.
