The Sun-Earth Thematic Action (ATST)

The Sun-Earth Thematic Action (ATST¹) is a component of the National Astrophysics Program (PN Astro) under the CNRS Earth and Universe Institute (INSU). The ATST aims to fund research projects and foster the national scientific community’s engagement with heliospheric plasma physics. The main themes of the ATST include:

• The Magnetic Sun – its interior and atmosphere – its activity and eruptions;
• The Solar Wind – from the Sun to the interplanetary medium – its origin, acceleration, and disturbances;
• Magnetospheres and Ionospheres – of Earth, the solar system’s planets, and exoplanets – their responses to solar forcing and impulsive events;
• The Heliosphere – as a whole, including its interaction with the interstellar medium – the mechanisms shaping its structure;
• Space Weather – forecasting solar geoeffective disturbances, monitoring the Sun, the near-space environment, and their impacts on the various envelopes of the Earth and other planets.

A unique aspect of the ATST community is its focus on studying the fundamental physical processes occurring under a wide variety of physical conditions, as found in heliospheric plasmas. Specifically, it seeks to understand:

• How the solar dynamo operates and the flux emergence process works;
• How instabilities are triggered and how large-scale feedbacks occur in both fluid and collisionless regimes;
• What are the effects of atomic physics on ionization, radiative transfer, and light polarization;
• What mechanisms accelerate plasmas and energetic particles, and dissipate energy via shocks, magnetic reconnection, waves, and turbulence;
• How to translate fundamental research results into applied tools for space weather forecasting.

Footnote: ¹ The ATST originates from the former National Sun-Earth Program (PNST).