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

大气区域耦合、能量和动力学(CEDAR)计划是一个基础广泛的、社区指导的高层大气研究计划，旨在了解从低层大气向上穿过大气层电离上层并进入外层空间磁层区域的大气区域的行为。这项由该奖项资助的研究将分析过去25年来通过分布在加拿大中部的13个测速仪网络收集的吸收数据，相邻地点之间的典型空间间隔为500至2000公里。这些仪器以30兆赫的频率工作，在多个地点测量75至115公里高度范围(上D区和下E区)电子产生引起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产生电子的来源：1)光致电离和2)与磁层起源的离子和电子的沉淀有关的碰撞电离。相对于静止日曲线(与光致电离有关)，任何时刻地球表面上方接收到的无线电波能量的损失是与粒子进入该电离区的沉淀有关的吸收的量度。里程计吸收测量的校准将通过使用在辐射带中观察到的测得的沉淀电子通量和测得的俘获电子数来实现。这次校准将以磁层探测器的测量为依据，这些测量是通过使用复杂的地球磁场分布场线模型追踪Van Allen探测器和五颗THEMIS卫星上的卫星粒子能量探测器的位置得出的，以确定这些卫星在加拿大中部不同空间位置的现场测量的磁层足迹。为该校准过程选择里程计吸收数据的过程将提取与足迹位置与里程计视野的重合相关的那些吸光值。收集的里程计吸收数据将在统计意义上进行分析，以确定关于吸收的大小和形状的吸收特征与导致每个里程计点的颗粒沉淀到90公里区域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种关系是开发一个可能的替代物来表示引起粒子降水的磁层波活动的程度。另一种关系是根据观测到的吸收确定高空大气在几十keV到MeV能量范围内的高能电子的部分损失。这一奖项的更广泛影响将是加强测速网络，使之成为一种有用的工具，具有在地面和空间天气预报中成功应用的强大潜力。将里程计吸收与卫星测量的沉淀电子进行比较，可以在统计上建立里程计吸收信号的大小和形状与沉淀粒子的能谱之间的关系。该网络内不同测力计的吸收特征结果将用于绘制降水的纬度和磁性当地时间(MLT)分布图。将这些特征信号与陷阱布居测量结果进行比较，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沉淀在全球系统中的作用。这项研究将与当前太阳周期的衰落阶段相吻合，并将有助于展示低成本的电离层降水遥感如何有助于了解直接影响地面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.