CEDAR: Characterizing Electron Loss to the Atmosphere Using Multi-point Measurements From Riometers and Spacecraft

大气区域的耦合、能量学和动力学（CEDAR）计划是一个基础广泛、社区指导的高层大气研究计划，旨在了解大气区域的行为，从低层大气向上穿过电离的高层大气，进入外层空间的磁层区域。由该奖项资助的研究将分析过去25年来由分布在加拿大中部的13公里网络收集的吸收数据，相邻站点之间的典型空间间隔为500至2000公里。这些仪器工作频率为30兆赫，在75至115公里的高度范围内（上D区和下e区）测量由电子产生的地外宇宙噪声无线电波的信号吸收。在这个高度范围内存在两种电子产生源：1)光电离和2)与磁层起源的离子和电子的沉淀有关的撞击电离。相对于平静日曲线（与光电离有关），在任何一个时间，地球表面以上接收到的无线电波功率的损失是与粒子沉降到电离区域有关的吸收的量度。将利用在辐射带中观测到的沉淀电子的测量通量和捕获电子的测量居群，来校准辐射计的吸收测量值。这一校准将以磁层探测器的测量结果为基础，这些测量结果来自追踪范艾伦探测器和五颗THEMIS卫星上的卫星粒子能量探测器的位置，使用地球磁场分布的复杂场线模型来确定这些卫星在加拿大中部不同空间位置的磁层足迹。在标定过程中，选取里程计吸收数据的过程将提取与足迹位置与里程计视场重合相关的吸收值。将从统计意义上分析所收集的riometer吸收数据，以确定有关吸收大小和形状的吸收特征与每个riometer站点负责90 km区域颗粒降水的特定能带之间可能的因果关系。在这项研究中要寻找的一个关系是开发一种可能的代理，用于磁层波活动引起粒子降水的程度。另一个关系是根据观测到的吸收来确定在几十千电子伏特到千电子伏特能量范围内的高能电子到上层大气的分数损失。该奖项的一个更广泛的影响将是加强一个里程计网络，使其成为一个有用的工具，在地面和空间天气预报方面具有成功应用的巨大潜力。将里程计吸收与沉淀电子的卫星测量相比较，将提供里程计吸收特征的大小和形状与沉淀粒子的能谱之间的统计关系的发展。网络内不同里程计的吸收特征结果将用于绘制降水的纬向和磁地方时（MLT）分布图。将这些特征与捕获种群的测量结果进行比较，将量化电子能量损失对大气的重要性，这将有助于理解高能电子降水在全球系统中的作用。这项研究将与当前太阳周期的衰退期相吻合，并将有助于证明电离层降水的低成本遥感如何有助于理解直接影响地球和空间天气气候的过程。

The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) program, a broad-based, community-guided, upper atmospheric research program, is aimed at understanding the behavior of atmospheric regions from the lower atmosphere upward through the ionized upper layers of the atmosphere and into the magnetosphere region of outer space. The research funded by this award would analyze the absorption data collected over the past 25 years by a network of 13 riometers located distributed across central Canada with a typical spatial separation of 500 to 2000 km between adjacent sites. These instruments operate at 30 MHz and measure at multiple locations the signal absorption of extraterrestrial cosmic noise radiowave caused by electron production in the altitude range of 75 to 115 km (upper D- and lower E-regions). Two sources of electron production exist in this height range: 1) photoionization and 2) impact-ionization associated with the precipitation of ions and electrons of magnetospheric origin. The loss of the radiowave power received above the Earth's surface at any one time relative to a Quiet Day Curve (which is associated with photo-ionization) is a measure of the absorption to be associated with the precipitation of particles into this ionized region. Calibration of the riometer absorption measurements would be achieved by using measured fluxes of precipitating electrons and measured populations of trapped electrons observed in the radiation belts. This calibration would be based upon the magnetosphere detector measurements derived from tracing the positions of satellite particle energy detectors onboard the Van Allen Probes and the five THEMIS satellites using a sophisticated field-line model of the Earth's magnetic field distribution to determine the magnetospheric footprints of these satellites in situ measurements at various spatial locations across central Canada. The process of selection of riometer absorption data for this calibration process would extract those absorption values associated with the coincidence of the footprint positions with the riometer field of view. The riometer absorption data collected would be analyzed in a statistical sense to establish possible causal relationships between the absorption signature regarding size and shape of absorption and the particular energy band responsible for the particle precipitation into the 90 km region for each riometer site. One relationship that would be searched for in this research is the development of a possible proxy for the extent of magnetospheric wave activity causing the particle precipitation. Another relationship would be the determination from the observed absorption the fractional loss of energetic electrons in the range of tens of keV to MeV energies to the upper atmosphere. A broader impact of this award would be the enhancement of a riometer network as a useful tool with a strong potential for successful application in terrestrial and space weather forecasting. Comparing riometer absorption with satellite measurements of precipitating electrons will provide for the development statistically of a relationship relating the size and shape of riometer absorption signatures with the energy spectrum of the precipitating particles. The absorption signature results for the different riometers within the network would be used to develop maps of latitudinal and magnetic local time (MLT) distributions of precipitation. Comparison of these signatures with trapped population measurements will quantify the importance of the electron energy loss to the atmosphere, which will help understand the role of energetic electron precipitation in the global system. This study would be coincident with the declining phase of the current solar cycle and will help to demonstrate how low-cost remote sensing of ionospheric precipitation can help understand processes that directly affect the terrestrial and space weather climate.