VLF/LF Measurements of Ionospheric Effects Associated with Lightning, Whistlers and Energetic Electron Precipitation

这笔拨款将支持一项实验研究，研究与大气闪电放电和源自磁层的自然波爆发有关的电离层下层瞬态和局部扰动。最近的实验证据证明了低层电离层和中层大气在大气-电离层-磁层系统各部分之间耦合中的重要性。发生在对流层的闪电效应通过中间层与电离层耦合，产生电离层脉冲电场，改变电离层电子密度和电导率，并发射电磁哨声波。由于磁层相互作用而产生的高能辐射带粒子（哨声波和VLF发射的爆发）沉积到较低的电离层和中间层，引起二次电离、x射线、光发射和加热。本基金的目的是为了更好地了解磁层-电离层-中间层-对流层系统中向下和向上耦合的过程，以及这些过程对地球辐射带动力学的影响。瞬态扰动事件是通过对亚层VLF/LF无线电信号的振幅和相位的高分辨率测量来遥感的，这些信号对中间层和d区高度的电子密度扰动很敏感。在美国和加拿大选定地点同时进行的观测将用于调查：(i)事件发生和特征的地理分布和地磁共轭关系；（ii） VLF信号扰动事件与闪电放电的关联；（iii）与个别闪电和活跃雷暴中心相关的扰动电离层区域的空间结构；（四）大气放电在辐射带动力学中的作用。

This grant will support an experimental investigation of transient and localized perturbations of the lower ionosphere that occur in association with atmospheric lightning discharges and with natural wave bursts that originate in the magnetosphere. Recent experimental evidence has demonstrated the importance of the lower ionosphere and the middle atmosphere in the coupling between parts of the atmosphere-ionosphere-magnetosphere system. Lightning-induced effects occurring in the troposphere are coupled to the ionosphere through the mesosphere, creating impulsive ionospheric electric fields, altering ionospheric electron density and conductivity, and launching electromagnetic whistler waves. Energetic radiation belt particles precipitated as a result of magnetospheric interactions whistler waves and with burst of VLF emissions are deposited into the lower ionosphere and the mesosphere, causing secondary ionization, x- rays, light emissions, and heating. The aim of this grant is to gain better understanding of the processed of downward and upward coupling in the magnetosphere-ionosphere-mesosphere-troposphere system and of the effects of these processes on the dynamics of the earth's radiation belts. The transient perturbation events are remotely sensed by means of high resolution measurements of the amplitude and phase of subionospheric VLF/LF radio signals, which are sensitive to perturbations of electron density at mesospheric and D-region altitudes. Simultaneous observations at selected locations in the United States and Canada will be used to investigate: (i) the geographic distribution and geomagnetic conjugate relationships of event occurrence and characteristics, (ii) the association of VLF signal perturbation events with lightning discharges, (iii) spatial structure of perturbed ionospheric region(s) associated with individual lightning flashes as well as with active thunderstorm centers, and (iv) the role of atmospheric discharges in the dynamics of the radiation belts.