Title of HDR
Physical processes in the interplanetary medium.
Composition of the jury
- Petr Hellinger, Rapporteur, Astronomický ústav Akademie věd České Republiky
- Hervé Lamy, Rapporteur, Institut Royal d’Aéronomie Spatiale de Belgique
- Viviane Pierrard, Rapportrice, Université Catholique de Louvain
- Matthieu Kretzschmar, Examinateur, Université d’Orléans
- Benoit Lavraud, Examinateur, Laboratoire d’Astrophysique de Bordeaux
- Laurence Rezeau, Examinatrice, Sorbonne Université
Abstract
Although its mass and density are very low, the interplanetary medium is an important astrophysical object, because of the volume it occupies, the structuring of the planetary and cometary environments it implies, and the many astronomical phenomena (auroras, meteors, zodiacal light, etc.) it is responsible for. It is also an environment rich in information about plasma dynamics, a research laboratory for studying the interaction between non-colliding plasma and electromagnetic field under conditions that are inaccessible to laboratory measurement. The in-situ sounding of the interplanetary medium and the theoretical modelling that this sounding enables is the subject of the work that I will present, based largely on the surveys carried out by five space missions : the Helios, STEREO and Wind probes, as well as the Parker Solar Probe and Solar Orbiter missions.
The work presented is divided into two parts, the first dealing with the work I have carried out in recent years on interplanetary plasma, addressing the question of the origin of the solar wind through a study of the kinetic signatures of interchange reconnection in the low corona, and then questions specifically related to the radial expansion of plasma : To what extent does this deviate from adiabatic expansion, to what extent is it regulated by coulombic collisions, and how can we identify and quantify the angular diffusion processes acting on suprathermal electrons ? The second part will be devoted to the study of the zodiacal dust cloud : what do we know about its dynamics, and about the sources and sinks of this cloud in dynamic equilibrium ? This part will be devoted in particular to the in-situ study of the cloud using the measurements provided by the radio instruments onboard the STEREO, Wind and Solar Orbiter probes, which since the 2010s have provided many new measurements in a size range (10-100 nm) that has been little studied until now.
