Measuring atmospheric phenomena
The expertise of the CEA's military applications Division (Direction des Applications Militaires, DAM), in atmospheric phenomena, and in particular infrasonic wave propagation, is based on over 40 years of research concening the detection of nuclear explosions. This experience has won the division recognition for its work in setting up facilities for monitoring application of the CTBT (Comprehensive Test-Ban Treaty), and also placed it at the forefront of fundamental research on the atmosphere and the ionosphere.
What are infrasonic waves?

Infrasonic waves or infrasound are caused by disturbances of natural origin that occur in the atmosphere, such as volcanic eruptions, meteorological disturbances, magnetic thunderstorms, wind and ocean swell, and also by artificial sources such as quarry blasts, aircraft going through the sound barrier, or nuclear explosions.
These waves propagate in the atmosphere at the speed of sound at frequencies that are inaudible to the human ear (below 20 Hz). They propagate over long distances with little attenuation.

Infrasound and nuclear explosions
Nuclear tests conducted in the atmosphere can be detected thanks to the infrasonic waves emitted. As part of its monitoring task, one of the CEA's objectives is to detect and locate this infrasound source. We therefore use a highly sensitive pressure sensor, known as a microbarometer. This device is based on one of the technologies adopted for the CTBT International Monitoring System (IMS).

Thanks to its dense network of highly sensitive stations, the IMS (currently in the setup process) will enable infrasound sources to be located and characterized. This network currently enables french national data Centers (Centre National de Données, CND) to detect certain hitherto unidentified phenomena.

How does a microbarometer work?
The atmosphere and the ionosphere central to fundamental research

The phenomena that can disturb the atmosphere or the ionosphere, such as atmospheric or magnetic thunderstorms, are central to the fundamental research conducted by the DAM's environmental assessment and monitoring Department (Département analyse, surveillance, environnement, DASE). The researchers are particularly seeking to understand the different interactions between the atmosphere and the ionosphere.
Therefore, they are particularly interested in sprites (recently discovered light emissions above atmospheric thunderstorms). In order to observe these phenomena, no longer from the earth but from the International Space Station (ISS), the DASE researchers set up the LSO (Lightning and Sprite Observations) experiment in partnership with the CNES (French National Space Studies Center) and the LAM (Marseille Astrophysics Laboratory).

Find out more:

Infrasound in the atmosphere - Natural infrasound

Ocean swell and mountain waves

Atmospheric thunderstorms


Atmosphere - Ionosphere: disturbances and coupling

Sprites and associated phenomena

Ionospheric disturbances
Sensors and networks

The MB2000 microbarometer

The Tahiti IS 24 station