Analysis of Terrestrial Gamma-Ray Flashes

这项调查的重点是分析存档和正在进行的观测地球伽马射线闪光（TGFs），这是短暂的，但强烈的辐射爆发与闪电和地球轨道上可见的适当仪器的卫星平台。 这些伽马射线在20世纪90年代首次被发现，被认为是电子通过一个被称为“相对论性逃逸”的过程加速到非常高的能量的结果。“可以想象，它们可能是闪电的原因（作为触发器，首先克服空气的绝缘特性，允许更大的电流流动）或闪电的影响（由于主闪电放电建立的强电场区域内的二次击穿过程）。 确定哪种情况适用是这项工作的目标之一。 将分析来自三个航天器的关于TGF的数据：（1）康普顿伽马射线天文台（已不在轨道上），其BATSE仪器首先发现了TGF;（2）RHESSI（目前在轨道上），它是现有TGF观测的最大来源;（3）最近发射的GLAST航天器，它携带伽马射线爆发监测仪。 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TGF传播中的作用的光谱建模。 还计划用最近研制的低高度仪器的观测数据进行相互比较（ADELE，机载高能闪电发射探测器），这些数据将在2009年8月至9月期间在佛罗里达雷暴附近的NSF-NCAR GV飞机上进行。（通常与宇宙源有关的那种）可能是在地球大气层内与带电云结合产生的。 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TGF发射雷暴的情况下，可能会扩展到航空/人类安全问题。

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.