Analysis of Terrestrial Gamma-Ray Flashes

这项调查的重点是对地面伽马射线闪电的存档观测和持续观测进行分析。地面伽马射线闪电是与闪电有关的短暂但强烈的辐射爆发，可通过配备适当仪器的卫星平台从地球轨道上看到。这些伽马射线第一次被探测到是在1990年的《S》中，被认为是电子加速到非常高能量的过程中产生的，这个过程被称为“相对论失控”。可想而知，它们可能是闪电的原因(通过充当触发器，首先克服空气的绝缘特性，允许更大的电流流动)，或者是闪电的影响(由于主闪电放电建立的强电场区域内的二次击穿过程)。确定这些情况中的哪一种适用是这项工作的一个目标。将对来自三个航天器的TGFs数据进行分析：(1)康普顿伽马射线天文台(不再在轨)，其BATSE仪器最先发现了TGF；(2)RHESSI(目前在轨)，这是现有的TGF观测源中最大的来源；和(3)最近发射的GLAST航天器，它携带伽马射线暴监测仪器。计划要求对RHESSI观测到的所有事件的背景气象条件进行更完整的统计描述和调查，并将扩展到改进大气在转化生长因子传播中的作用的光谱模拟。还计划与最近开发的低空仪器(Adele，高能闪电发射的机载探测器)的观测进行相互比较，该仪器将于2009年8月至9月在佛罗里达州雷暴附近搭载NSF-NCAR GV飞机。这项工作的学术价值将集中在改善对地球大气中可能产生高能辐射(通常与宇宙源有关的那种)和带电云层的机制的物理理解。更广泛的影响将主要来自学生的参与，但可以想象的是，在飞机冒险接近产生转化生长因子的雷暴的情况下，可能会扩展到航空/人的安全问题。

This investigation is focused on analysis of both archived and ongoing observations of Terrestrial Gamma-ray Flashes (TGFs), which are brief but intense bursts of radiation associated with lightning and visible from Earth orbit by suitably instrumented satellite platforms. These gamma rays were first detected in the 1990's and are thought to result from electrons accelerated to very high energies through a process termed "relativistic runaway." They may conceivably be either a cause of lightning (by serving as a trigger that first overcomes the insulating property of air, allowing larger currents to flow) or an effect of lightning (owing to a secondary breakdown process within zones of strong electric fields set up by the main lightning discharge). Establishing which of these situations applies is one objective of this work. Data on TGFs from three spacecraft will be analyzed: (1) The Compton Gamma Ray Observatory (no longer in orbit), whose BATSE instrument first discovered TGFs; (2) RHESSI (currently in orbit), which represents the largest source of available TGF observations; and (3) the recently launched GLAST spacecraft, which carries the Gamma-ray Burst Monitor (GBM) instrument. Plans call for a more complete statistical description and survey of background meteorological conditions for all RHESSI-observed events, and will extend to improved spectral modeling of the atmosphere's role in TGF propagation. Intercomparisons are also planned with observations from a recently developed lower altitude instrument (ADELE, the Airborne Detector for Energetic Lightning Emissions), which will be carried aboard the NSF-NCAR GV aircraft in the vicinity of Florida thunderstorms during August-September 2009.The intellectual merit of this effort will center on improved physical understanding of mechanisms by which highly energetic radiation (of the sort generally associated with cosmic sources) may be generated within Earth's atmosphere in conjunction with electrified clouds. Broader Impacts will come primarily from student involvement, but could conceivably extend to issues of aviation/human safety in those instances where aircraft venture close to TGF-emitting thunderstorms.