Terrestrial gamma-ray flashes in the Fermi era: Improved observations and analysis methods
Terrestrial gamma-ray flashes in the Fermi era: Improved observations and analysis methods
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DOI：
10.1002/jgra.50205
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发表时间：
2013-06-01
影响因子：
2.8
通讯作者：
Hutchins, Michael L.
中科院分区：
文献类型：
--
作者：
Briggs, Michael S.;Xiong, Shaolin;Hutchins, Michael L.
一种新的数据模式和新的分析方法被用来检测地面伽马射线闪光（TGFs）与费米伽马射线爆发监测器（GBM）10倍，比以前更频繁。在1037小时的观测中，除了39个TGFs和两个地球电子束事件之外，还发现了384个新的TGFs，而这些事件是在没有新的数据模式和方法的情况下发现的。宇宙射线簇射被发现是一个重要的背景;它们在GBM和费米大面积望远镜量热计的数据中显示出特征签名，使它们能够被移除，留下的样本估计由大约98%的TGFs组成。该样品包括比以前发现的GBM更短的TGF。真实的持续时间分布可能包含额外的短TGF，因为GBM对它们的检测受到检测器死区时间的限制。这个样本的三分之一与来自全球闪电定位网络（WWLLN）的位置相匹配，这些位置的地图比航天器位置的地图更清楚地显示了地理和气象特征。使用闪电成像传感器的闪电率图评估固有的TGF率，考虑GBM的检测效率作为航天器源偏移的函数，从中我们估计全球TGF率约为每年40万。随着新模式下数据的不断产生，我们估计GBM每年将检测到大约850个TGFs。
A new data mode and new analysis methods are used to detect Terrestrial Gamma-ray Flashes (TGFs) with the Fermi Gamma-ray Burst Monitor (GBM) 10 times more frequently than previously. In 1037h of observations at times and over regions for which TGFs are expected, 384 new TGFs were found in addition to the 39 TGFs and two Terrestrial Electron Beam events already detected without the new data mode and methodology. Cosmic ray showers were found to be an important background; they show characteristic signatures in the data of both GBM and the Fermi Large Area Telescope Calorimeter that enable their removal, leaving a sample estimated to consist of approximate to 98% TGFs. The sample includes shorter TGFs than previously found with GBM. The true duration distribution likely contains additional short TGFs because their detection by GBM is limited by detector dead time. One-third of this sample has matches with locations from the World Wide Lightning Location Network (WWLLN)maps of these locations show the geographic and meteorological features more clearly than maps of spacecraft locations. The intrinsic TGF rate is evaluated using the lightning rate maps of the Lightning Imaging Sensor, accounting for the detection efficiency of GBM as a function of spacecraft-source offset, from which we estimate a global TGF rate of approximate to 400,000 per year. With continuous production of data in the new mode we estimate that GBM will detect approximate to 850 TGFs per year.