Gamma Ray Showers Observed at Ground Level in Coincidence With Downward Lightning Leaders
Gamma Ray Showers Observed at Ground Level in Coincidence With Downward Lightning Leaders
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DOI：
10.1029/2017jd027931
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发表时间：
2018-07-16
影响因子：
4.4
通讯作者：
Zundel, Z.
中科院分区：
文献类型：
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作者：
Abbasi, R. U.;Abu-Zayyad, T.;Zundel, Z.
望远镜阵列表面探测器（TASD）在闪电中观测到伽马射线阵雨的爆发与向下传播的负前导一致。TASD是一个700公里(2)的宇宙射线天文台，位于美国犹他州西南部。在2014年至2016年收集的数据中，利用三维闪电测绘阵列获得了三次产生阵雨的闪光的结构和时间发展的相关观测结果，并获得了另外七次闪光的电场变化测量结果，这两种情况都与TASD同时发生。全国雷电探测网络的信息也在整个过程中使用。阵雨以连续的2-5次短时间（10秒）爆发的形式出现，时间间隔为几百微秒，在云层对地面闪电开始时，在向下负导击穿的前1-2毫秒内，阵雨起源于离地面3-5公里的高度。阵雨足迹、相关波形和大气传播的影响表明，阵雨主要由向下的伽马射线组成。这已经得到了GEANT模拟研究的支持，该研究表明，对于16度半角光束，初级源通量相似或等于10(12)-10（14）个光子。我们得出的结论是，这些阵雨是地球上的伽马射线闪光，与卫星观测到的类似，但地面观测更能代表时间源的活动，也比卫星观测更敏感，因为卫星观测只能探测到最强大的地球伽马射线闪光。
Bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700-km(2) cosmic ray observatory located in southwestern Utah, USA. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower-producing flashes were obtained with a 3-D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases colocated with the TASD. National Lightning Detection Network information was also used throughout. The showers arrived in a sequence of 2-5 short-duration (10s) bursts over time intervals of several hundred microseconds and originated at an altitude of similar or equal to 3-5km above ground level during the first 1-2ms of downward negative leader breakdown at the beginning of cloud-to-ground lightning flashes. The shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward-beamed gamma radiation. This has been supported by GEANT simulation studies, which indicate primary source fluxes of similar or equal to 10(12)-10(14) photons for 16 degrees half-angle beams. We conclude that the showers are terrestrial gamma ray flashes, similar to those observed by satellites, but that the ground-based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful terrestrial gamma ray flashes.