Ground Level Measurements of Terrestrial Gamma Flashes

卫星对雷暴顶部产生的强烈毫秒级伽马射线闪光(陆地伽马闪光-TGFs)的观测表明，闪电可以将电子加速到非常高的能级，远远超过1亿电子伏特(MeV)。路易斯安那州立大学(路易斯安那州立大学)最近的一项实验表明，TGFs是由地球表面附近的闪电产生的，而且源处的伽马射线强度非常高。路易斯安那州立大学的转化生长因子和高能雷暴屋顶阵列(TETRA)显示了与附近闪电有关的地面TGFs的存在。该项目是一项后续实验，名为TETRA-II，目的是用改进的统计方法测量能量和强度谱，扩大能量范围，确定产生TGFs的高度，并首次提供相关的辐射和气象数据。TETRA-II将安装在波多黎各和牙买加的两个地点，这些地点的雷暴活动明显高于路易斯安那州目前的TETRA地点，卫星飞越这些地点将能够同时从地面和太空寻找TGFs。情报优点：卫星对TGFs的观测表明伽马射线和闪电之间存在联系。然而，通常情况下，很难将伽马射线事件与个别局部雷暴联系起来。TETRA报告的地面观测使人们有可能将伽马射线与距离探测器3英里或更近的闪电联系起来，并使开始研究与雷暴的详细雷达图像之间的相关性成为可能。TETRA-II将位于选定的闪电密度高和轨道上伽马射线卫星观测到的TGFs频率较高的区域；TETRA-II对于个别事件的统计数据比TETRA高5倍，而且能量范围更高(可达10 MeV)，以便能够将测量结果与模型预测进行比较；它将与本地低频(低频，~100 kHz)闪电探测器阵列和能够观测云内闪电的宽带全球和区域网络以及附近的雷达一起运行。因此，TETRA-II有望提供有关在闪电附近观测到的TGFs的独特和详细的新数据，提供关于高能辐射产生机制和与闪电事件联系的新信息。设备资金由路易斯安那州董事会提供，设备建造将由路易斯安那州立大学和附近两所HBCU(巴吞鲁日的南方大学和新奥尔良的泽维尔大学)的学生进行。路易斯安那州立大学的工作人员将进行初步设计，培训和监督学生，并监督施工。与此同时，波多黎各和牙买加的学生小组将部署和操作一系列低频闪电探测器，以便最后确定地点，探索两个地点的远程操作，获得闪电探测经验，并组织波多黎各和牙买加小组能够在外地对探测器进行持续维护和操作。在路易斯安那州的学生们进行了一年的初步探测器建造和测试后，探测器阵列将于2015年夏天部署。阵列将远程操作，数据分析将在路易斯安那州领导，波多黎各和牙买加的学生团队将做出贡献。初步结果预计将于2015年秋季公布。目标是使用TETRA-II为来自路易斯安那州立大学、南方大学、泽维尔大学、大学的学生提供研究机会。波多黎各大学和哥伦比亚大学。在牙买加的西印度群岛生活了至少5-10年。该实验还将有助于发展波多黎各和加勒比发展中国家(牙买加)的研究能力。国家科学基金的这项支持旨在为路易斯安那州立大学和大学提供业务资金。波多黎各人在巴亚蒙。牙买加的合作者将向美国国际开发署申请独立资金。

Satellite observations of intense millisecond flashes of gamma rays (Terrestrial Gamma Flashes - TGFs) produced at the tops of thunderstorms have shown that lightning can accelerate electrons to very high energy levels, well above 100 million electron volts (MeV). A recent experiment at Louisiana State University (LSU) has now shown that TGFs are produced by lightning near the Earth's surface, and that the gamma ray intensity at the source is extremely high. The TGF and Energetic Thunderstorm Rooftop Array (TETRA) at LSU shows the existence of ground-level TGFs associated with nearby lightning. This project is a follow-up experiment, TETRA-II, intended to measure the energy and intensity spectrum with improved statistics, extend the energy range, determine the height at which TGFs are produced, and provide for the first time correlated radiation and meteorological data. TETRA-II will be located at two sites in Puerto Rico and Jamaica, at locations where thunderstorm activity is significantly higher than at the current TETRA site in Louisiana and where satellite overflights will enable looking for TGFs simultaneously from the ground and from space.Intellectual Merit: Satellite observations of TGFs have shown the connection between the gamma rays and lightning. Typically, though, it is difficult to associate the gamma ray events with individual well-localized thunderstorms. The ground-level observations reported by TETRA have made it possible to associate the gamma rays with lightning within 3 miles or closer to the detectors, and have made it possible to begin to study the correlations with detailed radar images of the thunderstorms. TETRA-II will be located in a region chosen to have high lightning density and a high frequency of TGFs seen by orbiting gamma ray satellites; it will be designed to have a factor of 5 better statistics than TETRA for individual events and a higher energy range (up to 10 MeV) so that measurements can be compared to model predictions; and it will be operated in conjunction with both a local array of low frequency (LF, ~100 kHz) lightning detectors and broadband global and regional networks capable of observing intra-cloud in addition to cloud-to-ground lightning, together with nearby radar. As a result, TETRA-II is expected to provide unique and detailed new data about TGFs observed close to lightning, providing new information both about the production mechanisms of the high energy radiation and about the connection with the lightning events.Broader Impacts: TETRA-II will be built and operated largely by a student team. Equipment funds have been provided by the Louisiana Board of Regents, with the equipment construction to be performed by students from LSU and two nearby HBCUs (Southern University in Baton Rouge and Xavier University in New Orleans). LSU staff will do the primary design, train and supervise the students, and oversee the construction. At the same time, an array of low frequency lightning detectors will be deployed and operated by the student teams in Puerto Rico and Jamaica in order to make final determinations of the sites, explore remote operations at the two sites, gain experience with the lightning detection, and organize the Puerto Rico and Jamaica teams to be able to perform continued maintenance and operation of the detectors in the field. After a year of initial detector construction and testing by the students in Louisiana, the detector array will be deployed during the summer of 2015. The array will be operated remotely and the data analysis led from Louisiana, with contributions from the student teams in Puerto Rico and Jamaica.Initial results are expected by the fall of 2015. A goal will be to use TETRA-II to provide research opportunities for students from LSU, Southern, Xavier, Univ. of Puerto Rico, and Univ. of the West Indies in Jamaica for at least 5-10 years. The experiment will also contribute to the development of research capability in Puerto Rico and a developing nation in the Caribbean (Jamaica). This NSF support is intended to provide operating funds for LSU and the Univ. of Puerto Rico at Bayamon. The Jamaica collaborators will request independent funding from US-AID.