4: Gamma-ray flashes

What is the role of energetic particles from thunderstorms on geospace?

  • Determine the characteristics of terrestrial gamma-ray flashes (TGFs); their occurrence frequency, production altitude, spatial extent of its source region and spectral/spatial distribution of photons in a TGF.
  • Determine the relation between lightning and TGFs, timing and type of lightning.
  • Determine the strength of the electric fields necessary to accelerate sufficient electrons to reproduce the observed TGF spectra.
  • Determine if and how lightning streamer, leader, and current pulses contribute to the strong electric fields and energetic electron populations required for TGF production.
  • Determine the electron, positron and photon flux associated with TGFs and their implications for the atmosphere and geospace. This will be further studied under G3 to estimate possible chemical and temperature effects in the stratosphere and mesosphere.

This is an ERC Advanced Grant project: TGF-MEPPA the first 5 years. ERC grant agreement No. 320839. This is an ERC Advanced Grant project: TGF-MEPPA the first 5 years. ERC grant agreement No. 320839.

These science objectives will be explored by combining modelling of electron acceleration, X- and gamma-ray production
and propagation and lightning development with unprecedented measurements of TGFs and lightning from five different distances: 

  • 600 km – by applying a new search algorithm we have more than doubled the number of TGFs observed by RHESSI (Gjesteland et al., 2012), and we now have the largest database in the world of TGFs.
  • 350 km - from the International Space Station (ISS), where we are building an imaging Modular X- and Gamma-ray Sensor (MXGS) as part of Atmosphere-Space Interaction Monitor (ASIM, funded by ESA-ELIPS3, to be launched in 2014). This is the first instrument specially designed to measure TGFs and lightning discharges from space.
  • 35 km - from balloon altitude, where we will build a smaller version of MXGS for COBRAT, a French gondola to fly over Central America in 2014/2015. COBRAT will also measure effects on chemistry, an important input to G3.
  • 20 km from aircraft altitude, where we plan to fly a similar detector as for COBRAT. Hiring aircraft, building instruments and field trips are included in the BCSS budget.
  • 1 m - from high-resolution gamma-ray detectors placed near sparks produced by a 2 MV Marx generator at the University of Technology in Eindhoven, the Netherlands.

Go to Overview to read more about the G4 work.