关于暴时电离层电流分布的南北半球不对称性  

On the asymmetry of the storm-time current system in the ionosphere between southern and northern hemispheres

作　　者：沈长寿[1] 资民筠[1] 王劲松[1] 徐寄遥[2] 刘顺林[3] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]空间天气学国家重点实验室,北京100080 [3]中国极地研究中心,上海200129

出　　处：《地球物理学报》2006年第6期1573-1581,共9页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(40374058;40134020;40225011);国家重点基础研究专项基金(G2000078407)资助

摘　　要：采用国际上广泛认可的高层大气和电离层经验模式提供的各种参数，通过电离层电流连续方程，计算出强磁暴条件下6月至日和12月至日内，磁纬±72°和磁地方时00：00-24：00之间电离层电场、电流等的分布,计算中考虑了地磁和地理坐标间的偏离；除中性风场感生的发电机效应外，还包含了磁层耦合（极盖区边界的晨昏电场和二区场向电流）的驱动外源．结果表明，6月至日时，磁层扰动自极光区向中低纬的穿透情况在南、北半球内基本接近，北半球内略强；但12月至日时，呈现明显的不对称性，南半球的电流穿透远强于北半球，而电场的穿透则是在北半球更强．无论南北半球，在中高纬地区，午夜至黎明时段出现较强的东向电场分量。其E×B的向上漂移效应，正是解释我们以往不少研究现象中所期盼的物理机制．The parameters of the upper atmosphere and ionosphere, such as the neutral wind and conductance, deduced from widely accepted empirical models are used to calculate the distribution of the electric field and current between geomagnetic latitudes ±72° and 00：00 - 24：00 MLT on June- and December-solstices during strong storms in terms of the ionospheric current continuity equation. The deviation of geomagnetic and rotation axes of the earth is considered in the calculation. Except the dynamo effect induced by the neutral wind, the driving electric field across the polar cap and the region 2 field-aligned current, caused by the magnetospheric coupling, are also taken into account. The results show that on the June-solstice the penetration of magnetospheric disturbances from the auroral zone to mid- and low-latitude areas is similar between the southern and northern hemispheres, but is a bit little stronger in the northern one. On the December solstice, however,obvious asymmetry appeared. The penetration of disturbed current is much stronger in the southem hemisphere than that in the northem one, meanwhile the penetration of the electric field is stronger in the northern one. Independent of the southern or northern hemisphere, in the moderate high latitude areas the existence of a eastward electric field in the midnight-dawn region is an expected mechanism, which can be used to explain phenomena found many times in our previous works, due to its g x B upper-ward drift effect.

关 键 词：扰动电流系 电离层发电机 热层风场 电导率 磁暴 磁层耦合 极盖区边界驱动电场 场向电流 

分 类 号：P352[天文地球—空间物理学]