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

大气区域耦合、能量学和动力学（CEDAR）计划是一个基础广泛、由社区指导的高层大气研究计划，旨在了解从低层大气向上通过电离层上层大气进入外层空间磁层区域的大气区域的行为。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个riometers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。 这些仪器的工作频率为30兆赫，在多个地点测量75至115公里高度范围（D区上部和E区下部）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电子产生源：1）光致电离和2）与磁层起源的离子和电子沉淀有关的碰撞电离。 相对于静日曲线（与光电离相关），在任何一个时间在地球表面上方接收到的无线电波功率的损失是与粒子沉淀到该电离区域相关的吸收的量度。将通过使用测得的沉淀电子通量和在辐射带中观测到的测得的俘获电子数量来校准辐射计吸收测量值。这一校准将以磁层探测器测量值为基础，这些测量值是通过追踪货车艾伦探测器和五颗THEMIS卫星上的卫星粒子能量探测器的位置得出的，使用地球磁场分布的复杂场线模型确定这些卫星在加拿大中部不同空间位置的磁层足迹。 用于该校准过程的辐射计吸收数据的选择过程将提取与足迹位置与辐射计视场的重合相关联的那些吸收值。将从统计学意义上分析所收集的riometer吸收数据，以建立关于吸收的大小和形状的吸收特征与负责每个riometer站点90公里区域内粒子沉降的特定能带之间的可能因果关系。在这项研究中要寻找的一种关系是，发展一种可能的代用指标，来衡量磁层波活动造成粒子沉淀的程度。另一个关系是从观测到的吸收中确定能量在几十keV至MeV范围内的高能电子到高层大气的部分损失。 这一奖项的更广泛影响将是加强riometer网络，使其成为一种有用的工具，具有成功应用于地面和空间天气预报的巨大潜力。将riometer吸收与卫星测量的降水电子进行比较，将提供一种统计学上的关系，这种关系将riometer吸收特征的大小和形状与降水粒子的能谱联系起来。 网络内不同riometer的吸收特征结果将用于绘制降水的纬度和磁性当地时间分布图。这些签名与捕获人口测量的比较将量化电子能量损失到大气中的重要性，这将有助于了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活动周期的下降阶段相吻合，并将有助于证明低成本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.