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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2010 > Séminaires 2010 > Le jeudi 18 février à 11h

Le jeudi 18 février à 11h

Alessandro Retino (Austrian Academy of Sciences, Space Research Institute) - In-situ observations of magnetic reconnection in solar system plasma

Le jeudi 18 février à 11 h Palaiseau, salle de conférence du CPHT

Magnetic reconnection is a fundamental process occurring at boundaries between magnetized plasma that is responsible for major conversion of electromagnetic energy into thermal and kinetic energy of charged particles and for transport of particles across boundaries. Reconnection is important for laboratory, space and astrophysical plasma and has been widely observed in a large number of different plasma conditions. Furthermore reconnection plays a key role for understanding the Sun-Earth interaction – the so-called space weather - that can severely affect our planet.

Studying magnetic reconnection requires a strong synergy between theoretical models/ numerical simulations and observations. At present the best laboratory to observationally study reconnection is the near-Earth space where direct measurements of particle distribution functions and electromagnetic fields are available in-situ. These measurements are required to study and understand the basic physics of reconnection. In particular recent multi-point high-resolution measurements from ESA/Cluster and NASA/Themis spacecraft allow for the first time to distinguish spatial from temporal variations and to compute three-dimensional quantities.

Magnetic reconnection is an intrinsically multi-scale process where the small spatial and temporal scales are strongly coupled to large scales. Reconnection is initiated rapidly in small regions but affect large volumes of space for a long time. Thus in-situ observations of reconnection at different temporal and spatial scales are crucial.

Despite of much evidence of reconnection, a number of key issues are yet poorly understood. The large−scale evolution of reconnection, its microphysics, its role for energetic particle acceleration and its relation with turbulence are among the most important.

Here I show recent Cluster reconnection studies addressing such problems. I present evidence that reconnection is a continuous process in time at the Earth’s magnetopause lasting for several hours. I present examples of the microphysics of reconnection and show the properties of reconnection at ion scales. I present the experimental discovery of reconnection in turbulent plasma through observations in the terrestrial magnetosheath. I show examples of energetic electron acceleration during reconnection and demonstrate the detailed physics of several acceleration mechanisms.

I finally discuss the requirements for future spacecraft missions e.g. NASA/MMS and ESA/Solar-Orbiter as well as for improved theoretical models/numerical simulations to increase our current understanding of reconnection in particular concerning the physics of reconnection at electron scales and of the relationship between reconnection and turbulence.

Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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Mentions légales
Exploitant du site : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Hébergeur : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
Directeur de la publication : Pascal Chabert (Directeur)