Study of Cross Polar Cap Potential Behavior During Storms and Superstorms Using Defense Meteorological Satellite Program (DMSP) Data

太阳风与磁层耦合以及磁层与电离层耦合的关键特征之一是在极冠上施加的电位降。 这种电位降及其在极地电离层中的相关电位分布模式可作为太阳风和磁层之间耦合的替代测量。最近的工作表明，极地电离层在极端太阳风条件下的行为与平静时期和中等磁暴期间的行为不同，极端太阳风条件产生称为超级磁暴的非常大的磁暴。 看来，无论太阳风携带的电场驱动系统有多强，极冠电位降都会在一个设定的水平上饱和。此外，极帽本身的大小似乎在这些饱和的电位条件下停止扩张。了解极冠电位的行为和极冠本身的大小以及它们如何对太阳风驱动因素（太阳风电场和太阳风冲压压力）以及电离层电导率的变化作出反应，是了解这一现象的基本物理学和建立准确可靠的地球空间环境模型的关键。这一为期三年的项目将利用DMSP航天器提供的极地电离层参数数据库，探索极地电离层对常规风暴和极端超级风暴的反应。 该项目将建立一个经验模型，说明极冠的大小与极冠潜力和各种太阳风输入的大小之间的关系。将检查太阳风电场的中到高值的周期，以确定电势饱和开始出现的过渡区域。该项目还将比较Hill-Siscoe模型得出的电离层Pedersen电导率与使用AMIE得出的数值

One of the key features in the coupling of the solar wind to the magnetosphere and the magnetosphere to the ionosphere coupling is the electric potential drop imposed across the polar cap. This potential drop and its associated potential distribution pattern in the polar ionosphere serves as a proxy measurement of the coupling between the solar wind and the magnetosphere. Recent work has shown that the polar ionosphere behaves differently under the extreme solar wind conditions that produce the very large magnetic storms known as superstorms as compared with the behavior during quiet times and moderate magnetic storms. It appears that the polar cap potential drop saturates at a set level no matter how strong the system is driven by the electric field carried by the solar wind. In addition the size of the polar cap itself appears to stop expanding under these saturated potential conditions. Understanding the behavior of the polar cap potential and the size of the polar cap itself and how they respond to solar wind drivers (the solar wind electric field and the solar wind ram pressure) as well as to the changes in the conductivity in the ionosphere are key to understanding the underlying physics of the phenomenon and in developing accurate and reliable models of the geospace environment. This three-year project will use the database of polar ionospheric parameters from the DMSP spacecraft to explore the polar ionosphere's response to regular storms and to the extreme superstorms. The project will develop an empirical model of the size of the polar cap as a function of the magnitude of the polar cap potential and various solar wind inputs. Periods of medium to high values of the solar wind electric field will be examined to determine the transition region where the saturation of the potential begins to appear. The project will also compare the ionospheric Pedersen conductivity derived from the Hill-Siscoe model with the value derived using the AMIE