2003年11月超强磁暴热层大气密度扰动及其与焦耳加热和环电流指数的关系——CHAMP卫星观测

本文利用CHAMP卫星加速度仪测量数据，计算和分析2003年11月20～21日大磁暴期间大气质量密度扰动的全球分布特征；研究暴时变化与极区大尺度对流引起的全球焦耳加热总功率及环电流指数SYM H之间的关系.结果表明，磁暴期间400 km高度上热层大气质量密度大幅度上升， NRLMSISE 00模式预测值与此相比有很大差别；暴时大气密度的增大存在昼/夜半球不对称性：白天强于夜晚，且白天随纬度的分布呈现出比较复杂的图像，在赤道附近和南半球中低纬区（10°N ～50°S）大气密度增大较强，并呈双峰分布，两个峰分别位于0°和45°S，另外在极区也出现大气密度扰动的局部极大，而在夜晚，大气密度变化南北半球比较对称，在赤道低纬区大气密度增大较强；互相关分析表明，中低纬区大气密度变化滞后于全球焦耳加热总功率3～7 h，滞后于环电流指数（SYM H）0～3 h，与二者存在很强的相关，表明极区焦耳加热和赤道环电流过程对暴时热层大气密度扰动有重要影响.

Changes of thermospheric mass density and their relations with Joule heating and ring current index during Nov. 2003 superstorm——CHAMP Observations

With the measurements by the accelerometer on board CHAMP during the severe geomagnetic storm occurring on November 20 21, 2003, the global distribution of the storm time changes in thermospheric total mass density at about 400 km height has been calculated and analyzed. 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 are investigated. It is found that the total mass density observed by CHAMP increased greatly during the November 2003 super storm, showing dramatic deviation from that predcted by NRLMSISE 00 model. The CHAMP observed increases of the total mass density exhibit strong day night asymmetry. On the dayside, it is stronger than that on the nightside, and shows a more complicated pattern versus latitude. Near the equator and at middle low latitudes in the southern hemisphere (10°N～50°S), the mass density enhancements are obviously stronger and show double peak likedistribution with two peaks lying at the equator and 45°S latitude respectively.In addition, the strongest local maximum of the density enhancement occurred in the polar region. On the night side, the change of the density is somewhat hemispheric symmetrical in comparison with that on the dayside and the augment is stronger at low latitudes. By cross correlation analysis it is found that the change of the total mass density lags behind the Joule heating by 3～7 hours and behind the ring current index（SYM H）by 0～3 hours. The close correlations between the changes and the Joule heating, as well as with the SYM H index, indicate that the massdensity changes during the magnetic storm largely depended on both the polar Joule heating and the low latitude processes associated with equatorial ring current.