Abstract
Understanding extreme space weather events is of paramount importance in
efforts to protect technological systems in space and on the ground.
Particularly in the thermosphere, the subsequent extreme magnetic storms
can pose serious threats to low-Earth orbit (LEO) spacecraft by
intensifying errors in orbit predictions. Extreme magnetic storms
(minimum Dst $\leq$ –250 nT) are extremely rare: only
7 events occurred during the era of spacecraft with high-level
accelerometers such as CHAMP (CHAllenge Mini-satellite Payload) and
GRACE (Gravity Recovery And Climate experiment), and none with minimum
Dst $\leq$ –500 nT, here termed magnetic superstorms.
Therefore, current knowledge of thermospheric mass density response to
superstorms is very limited. Thus, in order to advance this knowledge,
four known magnetic superstorms in history, i.e., events occurring
before CHAMP’s and GRACE’s commission times, with complete datasets, are
used to empirically estimate density enhancements and subsequent orbital
drag. The November 2003 magnetic storm (minimum Dst = –422 nT), the
most extreme event observed by both satellites, is used as the benchmark
event. Results show that, as expected, orbital degradation is more
severe for the most intense storms. Additionally, results clearly point
out that the time duration of the storm is strongly associated with
storm-time orbital drag effects, being as important as or even more
important than storm intensity itself. The most extreme storm-time
decays during CHAMP/GRACE-like sample satellite orbits estimated for the
March 1989 magnetic superstorm show that long-lasting superstorms can
have highly detrimental consequences for the orbital dynamics of
satellites in LEO.