We will explore how lightning are related to the production of high-energy gamma-rays within thunderstorms. We will do that by flying a high-altitude research aircraft over storms. From the aircraft, we will measure light, gamma-rays and electric field. From the ground, we will observe the structure of lightning. By putting together these measurements we will understand when, where and how lightning produce high-energy radiation.
Why is it important? A thunderstorm can act as the most energetic natural particle accelerator on earth, producing radiation with energy up to 500 times that of a normal chest X-ray radiography. There are on average 2000 storms active at any given moment on earth, and about 50 lightning per second. Radiation can therefore be very common, but the relation between lightning and radiation production is so far not fully understood. Radiation is related to the most common type of lightning and is then produced in very short bursts, less than one millisecond in duration, so bright that it can be detected from space. However, radiation can also be produced over several minutes and over regions as large as hundreds of square kilometers. We don't know yet the true duration and full extension of these emissions, and if and how they can affect the local weather and, potentially, climate.
A thunderstorm is the birthplace of the most energetic natural particle acceleration process on Earth. Terrestrial Gamma-ray Flashes (TGFs) and gamma-ray glows are manifestations of these acceleration process. Lightning, TGFs and glows are closely related but their precise relationship is still unknown. A missing link is in-situ observations close to the thunderclouds where these high-energy phenomena are produced.
Our ambition is to gather and analyze the first multi-wavelength observations of TGFs and glows from an aircraft (gamma-rays, optical, electric field), coordinated with ground-based radio observations. Our objective is to understand the processes and dynamics of lightning that lead to the production of TGFs, and their relationship with gamma-ray glows. It will solve a long standing scientific puzzle and shed light on the physics of intracloud discharges, which are the most common type of lightning on Earth. Quantification of the effects of TGFs and glows on local thundercloud chemistry and dynamics, may also have further impacts on atmospheric electricity, atmospheric sciences, and climate research.