Collaborative Research: Ground-based Very Low Frequency (VLF) and High Frequency (HF) Measurements in Support of the VIPER Sounding Rocket Experiment

合作研究：支持 VIPER 探空火箭实验的地基甚低频 (VLF) 和高频 (HF) 测量

• 批准号: 1952465
• 负责人: Robert Marshall
• 金额: $ 8.29万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-03-15 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952465&HistoricalAwards=false
• 关键词: Collaborative; Research; Ground; based; Very

Radio emissions in the Very Low Frequency (VLF) range are known to propagate long distances bouncing between the surface of the Earth and the partially ionized layer of the upper atmosphere near 90 km in altitude called the D region. The D-region impacts long range radio communications between extremely low frequencies (ELF), used for long-range submarine communications, and high frequencies (HF), used by many critical communications systems. VLF emissions can also escape the ionospheric layer and propagate to much higher altitudes with denser plasma. VLF emissions of both natural and man-made origin can also cause wave-particle scattering in the magnetosphere resulting in particle precipitation in the ionosphere. VLF radio wave propagation and signal strength reduction has been challenging to model and observe, mostly due to the lack of continuous measurements in the D region and significant uncertainties in the knowledge of both plasma and neutral densities at these altitudes. In this project, an enhancement will be made to the existing VLF Trans-Ionospheric Propagation Experiment Rocket (VIPER) experiment, to launch from Wallops Island in July 2020. VIPER will provide important information about radio waves detected along its trajectory, enabling a determination of the VLF attenuation through the ionospheric D region. Specifically, this project will support the installation of ground-based VLF and HF receivers near the transmitter site to provide ground-truth measurements to compare to the rocket measurements. These ground measurements will constrain the ionospheric state and will enable an accurate assessment of the attenuation of the VLF wave as a function of altitude. This project will also support the education of a student at CU Boulder, the training of a postdoc at CU Boulder and a postdoc at UC Berkeley, enhancing their continuing educations and providing a unique opportunity to learn about the valuable work at Wallops Flight Facility.This collaborative effort with provide direct multi-point measurements of VLF wave amplitude and phase, referenced directly from the source transmitter. VIPER will measure the height-resolved amplitude and phase of the NAA (24.0 kHz) transmitter signal broadcast from Cutler, Maine, enabling a determination of the VLF attenuation through the collisional D-region ionosphere. VIPER will also measure the plasma density and HF signal amplitudes during the ionospheric traverse. Together with the rocket measurements, we will have VLF measurements at the transmitter; downrange on the ground; and downrange as an altitude profile from 60 to 150 km. These measurements will provide unprecedented insight into the attenuation of VLF waves by the collisional D-region plasma. In turn, this attenuation will yield insight into the effect of ground-based transmitter signals on the D-region ionosphere and their injection into the magnetosphere. The project also has the potential to make measurements of lightning sferics (on the ground) and whistlers (above the ionosphere), providing a broadband (DC to MHz) view of this attenuation. The lightning observations are a secondary goal and are not critical to the success of the project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

众所周知，甚低频 (VLF) 范围内的无线电发射会在地球表面和海拔接近 90 公里的高层大气部分电离层（称为 D 区域）之间反弹长距离传播。 D 区影响用于远程海底通信的极低频 (ELF) 和许多关键通信系统使用的高频 (HF) 之间的远程无线电通信。 甚低频发射还可以逃离电离层并通过更密集的等离子体传播到更高的高度。自然和人造来源的甚低频发射也会引起磁层中的波粒散射，从而导致电离层中的粒子沉淀。 VLF 无线电波传播和信号强度降低一直难以建模和观察，主要是由于 D 区域缺乏连续测量，以及这些高度的等离子体和中性密度知识存在显着的不确定性。在该项目中，将对现有的 VLF 跨电离层传播实验火箭 (VIPER) 实验进行改进，将于 2020 年 7 月从瓦洛普斯岛发射。VIPER 将提供沿其轨迹检测到的无线电波的重要信息，从而能够确定通过电离层 D 区域的 VLF 衰减。具体来说，该项目将支持在发射机站点附近安装地面甚低频和高频接收器，以提供地面实况测量结果，以便与火箭测量结果进行比较。这些地面测量将限制电离层状态，并将能够准确评估 VLF 波的衰减随高度的变化。该项目还将支持科罗拉多大学博尔德分校学生的教育、科罗拉多大学博尔德分校博士后和加州大学伯克利分校博士后的培训，加强他们的继续教育，并提供独特的机会来了解沃洛普斯飞行设施的宝贵工作。这项合作提供了直接从源发射器参考的甚低频波幅度和相位的直接多点测量。 VIPER 将测量从缅因州卡特勒广播的 NAA (24.0 kHz) 发射机信号的高度分辨幅度和相位，从而确定通过碰撞 D 区电离层的 VLF 衰减。 VIPER 还将测量电离层穿越过程中的等离子体密度和高频信号幅度。 与火箭测量一起，我们还将在发射机上进行甚低频测量；地面下射程；向下范围为 60 至 150 公里的高度剖面。这些测量将为碰撞 D 区等离子体对 VLF 波的衰减提供前所未有的见解。反过来，这种衰减将深入了解地面发射机信号对 D 区电离层及其注入磁层的影响。该项目还有可能对雷电（地面）和哨声（电离层上方）进行测量，提供这种衰减的宽带（直流至兆赫）视图。 闪电观测是次要目标，对于项目的成功并不重要。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

An Electron Density Model of the D‐ and E‐Region Ionosphere for Transionospheric VLF Propagation

用于跨电离层甚低频传播的 D 区和 E 区电离层电子密度模型

• DOI: 10.1029/2021ja029288
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Space Physics
• 作者: Xu, Wei;Marshall, Robert A.;Bortnik, Jacob;Bonnell, John W.
• 通讯作者: Bonnell, John W.