The major scientific questions of the discipline are addressed through four distinct but complementary approaches, reflecting the community and international projects.
a) Through the study of astrophysical objects:
– The magnetic Sun – its interior, interfaces and atmosphere;
– The solar wind – from its birth on the Sun to the far reaches of the heliosphere;
– Magnetospheres – including the ionospheres of the Earth, planets and exoplanets;
– The heliosphere – up to its interaction with the interstellar medium.
b) Through fundamental plasma physics:
– How does the dynamo work, the solar cycle and the process of magnetic flux emergence?
– How are instabilities and scale couplings triggered in space plasmas?
– What are the effects of atomic physics on ionization, radiative transfer and light polarization?
– What are the mechanisms of particle acceleration and energy dissipation through shocks, magnetic reconnection, waves and turbulence?
– What are the local and global mechanisms that structure the heliosphere and its interaction with the interstellar medium?
d) Through societal applications in space weather:
– How can we predict the triggering and propagation of flares, coronal mass ejections (CMEs), solar energetic particles (SEP), and co-rotating interaction regions (CIRs)?
– What is the impact of solar disturbances (light, energetic particles, CMEs and solar wind) on geomagnetic, atmospheric and human activities?
– What are the long-term trends governing space climatology?
Interface activities
The ATST community also has numerous activities at the interfaces with other thematic actions (AT) of the astrophysics national program (PN Astro), other national programs (PN), CNRS institutes, and more. The most dynamic interfaces are to be found in the following fields:
a) Plasma physics:
Electrical phenomena in the upper atmosphere (INSU-OA); Magnetic confinement and acceleration, shocks and reconnection in laboratory plasmas, turbulence (INSIS & INP); Astrophysical plasmas (INSU-AA) including pulsars and cosmic rays (ATHE); Regional plasma physics initiatives (Plas@Par in Île-de-France).
b) Exploration of the solar system and its outer reaches:
Magnetospheres, exospheres and ionized environments of other planets in the solar system, their moons and comets (PNP), which are now a major component of ATST research; Boundaries and outer regions of the heliosphere, and its interaction with the interstellar medium (PCMI).
c) Physics of stars and their environment:
Stellar activity, including solar-type stars, surface magnetic fields and flares; Couplings between stellar winds and exo-planets; Exo-planetary magnetospheres (ATPS).
d) Space weather:
Some institutes have strong interfaces, even internally, with space weather applications on the inner magnetosphere and ionosphere (ONERA, CEA), or geomagnetism (INSU-OA, TS); National (INSU-OFRAME, CNES-GCME, DGA) and European (ESA-SSA & E-SWAN) space weather organizations.