GEM: Correlative Ground Based and Satellite Investigations of the Dynamics of the Nightside Open/Closed Magnetic Field Line Boundary

GEM计划的第二个主要观测和分析活动将是关于磁尾和亚暴的物理。磁层-电离层耦合的一个关键问题是确定磁力线从磁层的什么位置映射到夜间极光电离层。当磁层结构在这种周期性的能量释放过程中发生重大变化时，这个问题对于理解亚暴动力学变得更加重要。Burke等人最近的一项研究。1993A已经确定了夜间极光区的高纬度边界是与地磁尾部遥远的x线磁连接的。这标识了磁尾磁力线的开放/闭合边界。我们建议使用DMSP卫星数据和Svalbard和Sondrestrom的地面数据进行相关分析，以确定这两个数据集中共同看到的这一边界的特征，尽可能利用GEOTAIL数据确认对该边界的磁层解释，并解决该边界的空间和时间变化。来自斯瓦尔巴特群岛和格陵兰群岛的网络或极光电视和子午线扫描测光仪的光学数据将与Sondrestrom的雷达数据结合起来，与DMSP卫星数据进行比较。测量离子漂移、等离子体特征和高能粒子沉淀的三颗DMSP卫星目前持续监测高纬度电离层。直接头顶传球将建立关键签名。然后，可以利用空间上分离的数据集来确定该边界的空间和时间动态。这些结果的应用将对亚暴期间的地尾构型施加限制，并将有助于发展亚暴过程的模式。我们计划两个观察期：1994年1月和1994年12月至1995年1月。第一次恰逢计划中的宝石世界日期间，当时GEOTAIL在接近午夜的时候达到了100R的最高值。第二个对应于额外地面数据的特殊观察期。我们建议与其他GEM调查人员合作，共同定义和分析旨在阐明亚暴和地尾物理的特别活动事件。

The GEM program's second major observational and analysis campaign will be on the physics of the magnetotail and substorms. A critical question for magnetosphere-ionosphere coupling is to determine from where in the magnetosphere do magnetic field lines map to connect to the nighttime auroral ionosphere. This question becomes even more important for understanding substorm dynamics when significant changes to the magnetospheric configuration occur during this episodic release of energy. A recent study by Burke et al. 1993a has identified the high latitude boundary of the nighttime auroral region as magnetically connecting to the distant x-line in the geomagnetic tail. This identifies the open/closed boundary for magnetotail magnetic field lines. We propose a correlative analysis effort using DMSP satellite data and ground- based data from Svalbard and Sondrestrom to determine the characteristics of this boundary as seen jointly in both data sets, to confirm the magnetospheric interpretation of the boundary where possible using GEOTAIL data, and to resolve the spatial and temporal variations of this boundary. Optical data from a network or auroral TV and meridian scanning photometers in Svalbard and Greenland will be combined with radar data from Sondrestrom to compare with DMSP satellite data. Three DMSP satellites measuring ion drift, plasma characteristics and energetic particle precipitation currently monitor the high latitude ionosphere continuously. Directly overhead passes will establish critical signatures. The spatial and temporal dynamics of this boundary can then be determined with spatially separated data sets. Application of these results will place constraints on the geotail configuration during substorms and will aid in the development of a model of the substorm process. We plan two observation periods: January 1994 and December 1994 through January 1995. The first coincides with the planned GEM World Day period and when GEOTAIL is at an apogee of 100 R near midnight. The second corresponds to special observation periods for additional ground-based data. We proposed to collaborate with other GEM investigators to jointly define and analyze special campaign events for elucidation of substorm and geotail physics.