Observations and mechanisms of thunderstorm lightning effects in the lower ionosphere

As a violent energy release process in the troposphere, the effects of thunderstorms extend far beyond the lower atmosphere. Through mechanisms such as Transient Luminous Events (TLEs), Atmospheric Gravity Waves (AGWs), and various forms of energetic particle precipitation (particularly lightning-induced electron precipitation, LEP), thunderstorms establish a multi-layer coupling link extending from the troposphere directly to the ionosphere and even magnetosphere. This paper provides a systematic review of the latest observational evidence and mechanistic research regarding the impact of thunderstorms and lightning on the upper atmosphere. First, focusing on the TLEs such as Sprites, Elves (Emission of Light and Very-low-frequency perturbations due to Electromagnetic pulse Sources), and Gigantic Jets (GJs), we discuss their transient modulation effects on the conductivity and electron density distribution of the lower ionosphere (D-region) across various spatiotemporal scales. On this basis, the electromagnetic and mechanical mechanisms of upward energy transfer via quasi-electrostatic (QE) fields, electromagnetic pulses (EMP), and dynamical waves are analyzed. Subsequently, integrating Very Low Frequency (VLF) remote sensing technology, the scientific value of Early VLF perturbations and LOng Recovery Events (LORE) in diagnosing the lower ionosphere disturbances is summarized. Finally, in the framework of the context of the Global Electric Circuit (GEC) balance and the chemical evolution of the middle and upper atmosphere, the paper identifies key challenges and future directions for research, including multi-instrument observations, multi-physics coupled numerical simulations, and feedbacks within the climate change.