Collaborative Research: Strategic Observations of Terrestrial Gamma-Ray Flashes and Related Phenomena

该奖项支持对在雷暴内部产生的一小部分闪电中产生的地面伽玛射线闪光（TGFs）的研究。tgf是非常强大的伽马射线爆发；伽马射线是不可见光的粒子，类似于x射线，但在这种情况下，其能量比医生和牙医使用的x射线高出约100倍。虽然tgf很罕见，但被这些闪光直接击中一架满载乘客的飞机的后果是严重的。机组人员和乘客可能会突然受到非常高剂量的危险辐射，可能足以立即引起辐射病，并在以后的生活中患癌症的风险很大。大气物理学中关于tgf的一个尚未解决的有趣问题是tgf如何产生、为什么产生以及何时产生。研究小组试图了解伽马射线是如何变得如此明亮的，以及为什么（幸运的是）它们只发生在一千次闪电中的一次，这是基于他们目前对TGF的“构建模块”的理解，以及闪电期间如何自然发生高能辐射。这项调查将有可能使研究小组预测tgf与与飞机相互作用的闪电的关系，并为公共安全提供有关航空风险的宝贵信息。在这个项目中，研究小组将部署大量的伽马射线探测器（以前是由美国国家科学基金会、美国国家航空航天局和空军资助建造的）到地面站点、飞机和高空气球上，以便在以前看到过tgf的地方收集新的数据，比如冬天的日本西海岸、夏天的佛罗里达雷暴和飓风眼壁。每个地点和观察方法都选择在接近其生产地点的地方进行tgf的测量。关键的观察之一是tgf能达到多亮多暗。目前主流模型预测的TGF辐射强度的时间变化存在较大的不确定性。考虑到辐射强度随时间可能出现的一系列快速爆发，为了解决这种不确定性，将使用塑料闪烁体的快速响应探测器来观察每个伽马射线相互作用，以确定正确的模型物理。将闪电特征的测量（主要是通过无线电发射）与补充的气象数据相结合，该团队不仅能够了解产生TGF的闪电的详细行为，还能够了解没有产生TGF的情况下类似高质量的闪电数据，这一点同样重要。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports investigation of understanding terrestrial gamma-ray flashes (TGFs) generated among a small fraction of lightning flashes generated inside thunderstorms. TGFs are extraordinarily powerful bursts of gamma radiation; gamma-rays are particles of invisible light, similar to x-rays but in this case with energies up to about 100 times higher than the x-rays used by doctors and dentists. Although TGFs are rare, the consequences of a direct hit by one of these flashes to a plane full of people are significant. The crew and passengers could receive a very high, sudden dose of dangerous radiation, possibly enough to cause immediate radiation sickness and a significant risk of cancer later in life. An unsolved and interesting problem in atmospheric physics regarding to TGFs is how, why, and when TGFs are produced. The research team seeks understanding of how the gamma-rays get as bright as they do and why (fortunately) they only happen in maybe one out of a thousand lightning flashes based on their current understanding of the ``building blocks'' of a TGF and how high-energy radiation might naturally happen during lightning. The investigation will potentially enable the team to predict involvement of TGFs in lightning flashes that interact with aircraft and provide valuable information on aviation risks for public safety. In this project, the research team will deploy a number of gamma-ray detectors (previously constructed under funding from NSF, NASA, and the Air Force) to ground-based sites, aircraft, and high-altitude balloons in order to gather new data on TGFs in places they have been seen before, such as the western coast of Japan in winter, summer thunderstorms in Florida, and the eyewalls of hurricanes. Each site and the method of observation have been chosen for measurements of TGFs close to their production locations. One of the key observations will be how bright TGFs can get and how faint they get. Currently temporal variations of TGF radiation intensity predicted by leading models have significant uncertainty. To address this uncertainty with consideration of a possible series of rapid bursts of radiation intensity with time, the fast response detector of plastic scintillators for observing each gamma-ray interaction will be used to determine the correct model physics. Combining measurements of lightning characteristics (mostly via radio emission) with complementary meteorological data, the team would be able to understand not only the detailed behavior of lightning that produces TGFs, but also lightning data of similar high quality for situations where a TGF did not get produced, which is equally important to understand.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.