ASIM reveals the world's most extreme energy discharge

The ASIM observatory was launched in 2018 and mounted on the International Space Station (ISS) to observe and measure powerful lightning phenomena in the Earth atmosphere. Terma was the prime contractor of ASIM and maintains the technical responsibility for the mission.

With measurements from the Danish-led ASIM mission on ISS, an international research team headed by DTU Space at Technical University of Denmark has discovered that extremely energetic flashes of X-rays can be emitted from thunder clouds while illuminating a huge area of the lower ionosphere by UV radiation. The discovery has just been published in the scientific journal Science.

X -ray flashes from thunderclouds are called Terrestrial Gamma-ray Flashes (TGF) and have energies several thousand times higher than for example the X-ray used at the dentist.

Scientists have been trying to understand TGFs since they were discovered in 1994, but with ASIM they have come a big step closer to understanding the mechanisms behind. They are described in two additional articles, just published in the Journal of Geophysical Research.

ASIM was sent to ISS in April 2018 and was installed outside on the European Columbus module. From its orbit 400km above Earth, ASIM from it’s position on the European Columbus module has taken thousands of measurements of severe thunderstorms across the globe.

Terma is technically responsible for the observatory, while DTU Space is scientifically responsible for the ESA-led project. Both Terma and DTU Space have played crucial roles in the development of the advanced instruments included in the observatory.

“It was an exciting challenge for Terma to develop ASIM. Danish aerospace has with ASIM documented its expertise and the high scientific and technical level we master”, said Terma’s project manager Ole Hartnack in connection with the launch of ASIM.

About the just published scientific results, Torsten Neubert, who is scientifically responsible for ASIM and chief consultant at DTU Space, says: “Our measurements indicate that TGFs are created by electrons that are accelerated to very high energies in the electric field at the head of a lightning - just as it is taking a step forward. At the same time, the electrical impulse can be so powerful that it estimates a large part of the ionosphere at 90 km altitude. By getting above the clouds with ASIM, a whole new window has opened to the interior of amazing lightning and related phenomena."

The new discoveries were announced at the American Geophysical Union's Earth and Space Science Annual Meeting, held in San Francisco during week 50/2019.

ASIM's combination of instruments is based on expertise in Terma and DTU Space, and partners at the Universities of Bergen and Valencia. It is an impressive dedicated collaboration that has made it possible to observe both gamma-flashes and visible lightning at the same time.