Rapid recovery of thermosphere density during the October 2003 geomagnetic storms

Our results show that the relaxation times, defined by the e-folding time of the poststorm recovery of thermosphere density, are about 6 and 8 h for two recovery phases of the October 2003 superstorms, respectively. Geomagnetic activity index Kp or ring current index Dst is incapable of describing the rapid recovery of thermosphere density.

Moreover, a weak altitudinal dependence of the relaxation times was observed between the CHAMP and GRACE altitudes at middle and high latitudes, but no coherent latitudinal dependence was found. The MSISE00 and TIEGCM neutral densities are compared with the observations to assess their capability in predicting the thermosphere response during the recovery phase of extremely severe storms. Neither the MSISE00 nor the TIEGCM reproduced the rapid recovery of thermosphere densities seen in the CHAMP and GRACE, although the TIEGCM captured most of the salient features observed by CHAMP and GRACE when AMIE convection and precipitation patterns were used to specify the high-latitude drivers.