In this letter, we present for the first time the method to get insight into the charge structure of the thundercloud using simultaneously measured electron and gamma-ray energy spectra of the thunderstorm ground enhancement (TGE). We discuss and compare two main scenarios that can support the initiation of the relativistic runaway electron avalanches (RREA) in the thundercloud. One of the scenarios includes the emergence of the lower positive charged layer (LPCR). The LPCR is a short-living charge structure sitting on hydrometeors, which exhibit accidental charge reversals depending on temperature changes. LPCR can sustain a downwards directed near-surface electric field for several minutes, before falling down with precipitation. Recently, we launched on Aragats a large spectrometer, which is capable to measure energy spectra of electrons and gamma-rays in the energy range from 4 to 100 MeV. Comparison of energy spectra of electrons and gamma-rays makes it possible to scrutinize the LPCR emergence and estimate the height where the strong electric field that originates the RREA terminates.

在这封信中，我们首次介绍了使用同时测量的雷暴地面增强 (TGE) 的电子和伽马射线能谱来深入了解雷云电荷结构的方法。我们讨论并比较了可以支持在雷云中引发相对论失控电子雪崩 (RREA) 的两种主要场景。其中一种情况包括下正电荷层 (LPCR) 的出现。LPCR 是一种位于水凝物上的短寿命电荷结构，它会根据温度变化表现出意外的电荷反转。LPCR 可以维持一个向下的近地表电场几分钟，然后随着降水下降。最近，我们在 Aragats 上推出了一台大型光谱仪，它能够测量能量范围为 4 到 100 MeV 的电子和伽马射线的能谱。电子和伽马射线能谱的比较使得可以仔细检查 LPCR 的出现并估计产生 RREA 的强电场终止的高度。