Closed to Open: Particle Signatures Across a Topological Transition

粒子在闭合磁力线和开放磁力线上沉淀的性质是完全不同的，但是当磁力线首先从闭合磁力线转换到开放磁力线时沉淀所经历的转变还没有很好的理解。有几个重要的阶段，作为粒子沉淀的变化特性的开放/封闭的磁场边界（OCB），需要记录，调查和理解，因为这些变化的细节有重要的地球物理后果。该项目将根据低能离子截止等现象以及电子和离子反弹时间的基本计算，制定OCB中粒子特性转变的详细年表。所有这一切的结果将提供一个工具包，用于在OCB附近进行粒子观测。在将要研究的跃迁的详细方面中，高能磁层离子的退出是一个问题。在磁层顶部分反射的损失将导致最高能量的离子首先消失，而闭合场线的再补给将导致最高能量的离子持续最长时间。这两个过程的相对重要性尚不清楚。其他问题涉及高能磁层电子，它可能更密切地遵循对流反转边界，而不是OCB。高能电子的能量是否分散在OCB上，以及高能电子是否可以与磁鞘电子共存一段与通量管排空不一致的时间，目前还不清楚。其他很少讨论的影响包括出现的“影子”电子沉淀赤道的主要尖点（离子到达之前）。这个群体类似于极地雨或“strahl”电子。这个阴影区域的大小从几乎不存在到超过1度不等，原因不明。所有这些粒子特性的变化在整个OCB似乎有系统的规范和变量，这可能提供重要的线索，定量建模。结果也将用于调查低纬边界层开放或封闭的程度。该项目还将继续维护国防气象卫星计划（DMSP）资源，通过万维网分发粒子数据。该网站（http：//sd-www.jhuapl.edu/Aurora）为世界各地的研究人员提供了一个宝贵的工具。由于该网站提供的便利和帮助，研究生和博士后研究员是该系统的大量用户。

The nature of particle precipitation on closed and open magnetic field lines is quite different, but the transition that the precipitation undergoes when a magnetic field line is first converted from a closed field line to an open one is not well understood. There are several important stages as particle precipitation changes character across the open/closed magnetic field boundary (OCB) which need to be documented, investigated, and understood, because the specifics of these changes have important geophysical consequences. This project will develop a detailed chronology of the transition of particle characteristics across the OCB, based on phenomena such as the low-energy ion cutoff, and basic calculations of electron and ion bounce times. The result of all this will be to provide a toolkit for placing particle observations near the OCB in context. Among the detailed aspects of the transition that will be studied is the drop-out in high-energy magnetospheric ions. Loss at the magnetopause with partial reflection would lead to the highest energy ions disappearing first, while resupply from closed field lines would lead to the highest energy ions lasting longest. The relative importance of these two processes is not yet known. Other issues involve the high-energy magnetospheric electrons, which may more closely follow the convection reversal boundary rather than the OCB. Whether the energetic electrons are energy dispersed across the OCB, and whether the energetic electrons can co-exist with magnetosheath electrons for a time inconsistent with flux tube emptying is not yet known. Other little discussed effects involve the appearance of a "shadow" electron precipitation equatorward of the main cusp (before ions arrive). This population resembles the polar rain or "strahl" electrons. The size of this shadow region varies from virtually non-existent to more than 1 degree, for reasons unknown. All these changes in particle characteristics across the OCB seem to have systematic norms and variants, which may provide important clues for quantitative modeling. The results will also be of use in investigating the extent to which the low latitude boundary layer is open or closed. This project will also continue to maintain a Defense Meteorological Satellite Program (DMSP) resource, distributing particle data through the World Wide Web. The web site (http://sd-www.jhuapl.edu/Aurora) provides researchers around the world with a valuable tool. Because of the ease of access and aids provided at the web site, graduate students and postdoctoral fellows have been heavy users of the system.