Journal ArticleSource Altitude of Energetic In‐Cloud Pulses Inside Thunderstorms and Implication for the Intrinsic Brightness of Terrestrial Gamma‐Ray FlashesLyu, Fanchao [State Key Laboratory of Severe Weather &amp; CMA Key Laboratory of Lightning Chinese Academy of Meteorological Sciences Beijing China] (ORCID:0000000283357480); Qin, Zilong [Guangdong‐Hong Kong‐Macao Greater Bay Area Weather Research Center for Monitoring Warning and Forecasting (Shenzhen Institute of Meteorological Innovation) Shenzhen China] (ORCID:000000017499355X); Cummer, Steven A [Electrical and Computer Engineering Department Duke University Durham NC USA] (ORCID:0000000200020613); Zheng, Yu [Key Laboratory of Transportation Meteorology of China Meteorological Administration Nanjing Joint Institute for Atmospheric Sciences Nanjing China]; Jiang, Sulin [State Key Laboratory of Severe Weather &amp; CMA Key Laboratory of Lightning Chinese Academy of Meteorological Sciences Beijing China]; Zheng, Tianxue [State Key Laboratory of Severe Weather &amp; CMA Key Laboratory of Lightning Chinese Academy of Meteorological Sciences Beijing China] (ORCID:0000000194832905); Liu, Yan [Key Laboratory of Transportation Meteorology of China Meteorological Administration Nanjing Joint Institute for Atmospheric Sciences Nanjing China]; Xu, Wei [Electronic Information School Wuhan University Wuhan China] (ORCID:000000030092824X); Lyu, Weitao [State Key Laboratory of Severe Weather &amp; CMA Key Laboratory of Lightning Chinese Academy of Meteorological Sciences Beijing China] (ORCID:0000000184346655)<title>Abstract</title> <p>Upward Terrestrial Gamma‐Ray Flashes (TGFs) are mainly produced during the upward propagating negative leaders inside thunderclouds. The exact source position of TGFs, which is crucial to understanding TGF source properties, is still unclear. The link between positive energetic in‐cloud pulses (+EIPs) and TGFs provides us with a potential target to aim at. In this study, the low‐frequency radio emissions of 75 +EIPs are analyzed to retrieve the source altitudes with an improved ray theory model. Furthermore, the meteorology contexts of +EIPs derived from the ground‐based weather radars and satellite‐based infrared cloud top temperature measurements are investigated. +EIPs are produced at 8.8–13.7 km, with an average of 11.3 km inside thunderclouds, and at an average of ∼2.5 km below cloud tops. These altitudes indicate that a total number of 1.7 × 10¹⁶to 2.6 × 10¹⁸gamma ray photons with energy greater than 1 MeV are required for an EIP‐TGF to be measured by spaceborne detectors.</p>Wiley2024-10-2810666704Geophysical Research Letters51200094-8276https://doi.org/10.1029/2024GL1105982026304National Science Foundation