Lightning is often accompanied by the production of TGFs, which are intense bursts of gamma rays originating in the thundercloud region. These gamma-ray emissions are primarily produced by relativistic runaway electrons accelerated in the strong electric fields inside the cloud.
In addition to TGFs, lightning can also generate UV emissions in the ionosphere, located at altitudes of about 60-300 kilometers above Earth's surface. These UV emissions are known as lightning-induced electron precipitation (LEP) events and are caused by the interaction of high-energy electrons accelerated by lightning with the ionospheric atoms and molecules.
To study these phenomena, scientists used data from the Atmosphere-Space Interactions Monitor (ASIM) instrument onboard the ISS. The ASIM instrument is designed to observe transient luminous events (TLEs), including TGFs and sprites, and to investigate their relationship with lightning and other atmospheric processes.
By analyzing ASIM observations, researchers found that TGFs and LEP events can occur simultaneously with lightning. The TGFs are typically detected within a few milliseconds of the lightning flash, while the LEP events occur several milliseconds to a few seconds later. The duration of these UV emissions can vary from milliseconds to several seconds, providing additional insights into the complex processes occurring in the atmosphere during thunderstorms.
These findings shed light on the role of lightning in producing high-energy emissions and their impact on the Earth's atmosphere. Further studies and observations using instruments like ASIM will help deepen our understanding of the intricate connections between lightning, TGFs, and other transient luminous phenomena in the Earth's atmosphere.
