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

CEDAR：使用测距计和航天器的多点测量来表征大气中的电子损失

• 批准号: 1552321
• 负责人: Adam Kellerman
• 金额: $ 32.02万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1552321&HistoricalAwards=false
• 关键词: CEDAR; Characterizing; Electron; Loss; Atmosphere

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.

大气区域耦合、能量和动力学 (CEDAR) 计划是一项基础广泛、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层并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 年由分布在加拿大中部的 13 个测量仪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 MHz，可在多个位置测量 75 至 115 公里高度范围（上 D 区和下 E 区）内由电子产生引起的地外宇宙噪声无线电波的信号吸收。 在此高度范围内存在电子产生的两个来源：1) 光电离和2) 与磁层起源的离子和电子沉淀相关的碰撞电离。 相对于安静日曲线（与光电离相关），在任何时刻地球表面上方接收到的无线电波功率的损失是与粒子沉降到该电离区域相关的吸收的量度。辐射计吸收测量的校准将通过使用测量的沉淀电子通量和测量的在辐射带中观察到的捕获电子的数量来实现。该校准将基于磁层探测器测量结果，该测量结果是通过跟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而得出的，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原位测量的磁层足迹。 用于该校准过程的测量仪吸收数据的选择过程将提取与足迹位置与测量仪视场的重合相关联的那些吸收值。收集的辐射计吸收数据将以统计意义进行分析，以建立有关吸收大小和形状的吸收特征与负责每个辐射计站点的 90 公里区域中颗粒沉淀的特定能带之间可能的因果关系。本研究中要寻找的一种关系是开发一种可能的代理方法，来表示引起粒子沉淀的磁层波活动的程度。另一种关系是根据观测到的吸收来确定数十 keV 至 MeV 能量范围内的高能电子到高层大气的损失分数。 该奖项的更广泛影响将是增强测量仪网络作为一种有用的工具，在陆地和空间天气预报中具有成功应用的巨大潜力。将辐射计吸收与沉淀电子的卫星测量进行比较，将提供统计上发展的关系，该关系将辐射计吸收特征的尺寸和形状与沉淀粒子的能谱相关联。 网络内不同辐射计的吸收特征结果将用于绘制降水的纬度和磁本地时间（MLT）分布图。将这些特征与被捕获的粒子测量值进行比较将量化电子能量损失到大气的重要性，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周期的衰退阶段相一致，并将有助于证明电离层降水的低成本遥感如何帮助了解直接影响陆地和太空天气气候的过程。