Open/Closed Boundary and Energy Cutoff Latitude Data for Papers 1 and 2

Abstract for Paper 1 The open-closed boundary (OCB) defines a region of significant transformation in Earth's protective magnetic shield. Principle among these changes is the transition of magnetic field lines from having two foot points, one in each hemisphere, to one foot point at Earth, the other mapping to the solar wind (SW). Charged particles in the SW are able to follow these open field lines into Earth's upper atmosphere. The OCB also defines the polar cap boundary (PCB). Being able to identify and track the OCB allows study of several components of the geomagnetic system. Among them are the electrodynamics of the geomagnetic field and the reconnection balance between the dayside and nightside of the geomagnetic field. Furthermore, the OCB can provide interesting insights into the precipitation of energetic protons into the ionosphere. Using the Tsyganenko model of the geomagnetic field we demonstrate a diurnal fluctuation which we call the Universal Time (UT) effect of the OCB. This UT effect is independent of all other inputs. We anticipate this UT effect to have important consequences in modeling the OCB and other polar cap-associated structures, especially polar cap absorption (PCA) events which adversely affect high frequency radio wave propagation in polar regions. Abstract for Paper 2: The first well-documented polar cap absorption event occurred on 23 February 1956. Since that time much has been learned and explored regarding these events and their effect on high-frequency radio wave propagation in earth's polar regions. An important boundary when considering geomagnetic field topology and polar cap absorption events is commonly referred to as the cutoff latitude or energy cutoff latitude. The cutoff latitude is dependent on several factors, including solar wind parameters and proton energy. There exists an extensive body of research involving the cutoff latitude. One common approach in finding the cutoff latitude is to use a model of the geomagnetic field and trace proton trajectories through the field. Using this approach and the 1996 version of the Tsyganenko model, we demonstrate a unique method to organize three cutoff latitude boundary dependencies. The first, which we call a Universal Time or UT effect, is independent of proton energy and is based on geomagnetic alignment. The second, a local time or LT effect, exhibits an energy-dependent modulation as well as solar wind dependence. The third, a longitudinal effect, is also energy-dependent. Together, these effects can significantly alter the solar proton energy cutoff latitude, especially in the energy regime most responsible for polar cap absorption events.论文1摘要 开放-闭合边界 (open-closed boundary, OCB) 定义了地球防护磁层中发生显著变化的区域。其中最主要的变化是磁力线从拥有两个足点（分别位于南北两个半球）向单足点的转变：一个足点位于地球，另一个足点则映射至太阳风 (solar wind, SW)。太阳风中的带电粒子可沿这些开放磁力线进入地球高层大气。开放-闭合边界同时也是极盖边界 (polar cap boundary, PCB) 的界定边界。对开放-闭合边界进行识别与追踪，能够助力地磁系统多维度组分的研究，其中包括地磁场所涉及的电动力学过程，以及地磁向日面与背日面之间的重联平衡。此外，开放-闭合边界还可为高能质子向电离层的沉降过程提供极具价值的研究视角。本研究借助齐加年科地磁模型 (Tsyganenko Model)，证实了一种日变化波动现象，我们将其称为开放-闭合边界的世界时 (Universal Time, UT) 效应，该效应独立于所有其他输入变量。我们预计，这一世界时效应对开放-闭合边界及其他极盖相关结构的建模工作具有重要意义，尤其是会对极盖吸收 (polar cap absorption, PCA) 事件的建模产生影响——这类事件会对极地地区的高频无线电波传播造成不利干扰。 论文2摘要： 1956年2月23日发生了首例有完整记录的极盖吸收事件。自该事件以来，学界针对这类事件及其对地球极地地区高频无线电波传播的影响开展了大量研究与探索。在研究地磁场拓扑结构与极盖吸收事件时，一个关键边界通常被称为截止纬度或能量截止纬度。截止纬度受多种因素影响，包括太阳风参数与质子能量，目前已有大量围绕截止纬度展开的研究成果。确定截止纬度的常用方法之一是借助地磁场模型，通过追踪质子在场域中的运动轨迹来实现。本研究采用该方法，并结合1996版齐加年科地磁模型 (Tsyganenko Model)，提出了一种可梳理三种截止纬度边界依赖关系的独特方法。第一种效应我们称之为世界时 (UT) 效应，其与质子能量无关，仅由地磁对准特性决定；第二种为地方时 (LT) 效应，兼具能量依赖调制特性与太阳风依赖特性；第三种为经度效应，同样具有能量依赖性。这三种效应共同作用，可显著改变太阳质子能量截止纬度，尤其是在极盖吸收事件主要对应的能量区间内。