Changes of Thermospheric Mass Density and Their Relations with Joule Heating and Ring Current Index During Nov. 2003 Superstorm—CHAMP Observations

Abstract

AbstractUsing the accelerometer measurements on board CHAMP during the severe geomagnetic storm of November 20‐21, 2003, a study is made on the global distribution of the storm‐time changes in thermospheric total mass density at about 400 km height. The mutual relations of the storm‐time changes with the global integrated Joule heating power produced by large convective electric field, as well as with the ring current index of SYM‐H have also been investigated. It is found that the total mass density increased greatly during the November 2003 super‐storm, showing dramatic deviation from that predicted by NRLMSISE‐00 model. The density increases exhibit strong day‐night asymmetry, with larger augment and more complicated pattern versus latitude on the dayside. It shows a double peak‐like distribution at low‐mid latitudes with two prominent peaks at the equator and 45°S latitude respectively, while one of the strongest local maximum of the density enhancement occurs in the polar region. On the other hand, the density changes on the night‐side are somewhat hemispheric symmetrical in comparison with that on the dayside and the augment is stronger at lower latitudes. Elaborate cross‐correlation analyses reveal that the changes of the total mass density lag behind the Joule heating by 3~7 hours and behind the ring current index (SYM‐H) by 0~3 hours. The high correlation coefficients indicate that the mass density changes during the magnetic storm largely depend on both the polar Joule heating and the low‐latitude processes associated with the equatorial ring current.