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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2016 > Séminaires 2016 > Le Mercredi 10 Février à 11h

Le Mercredi 10 Février à 11h

Gaétan le Chat (LESIA, Obs. de Meudon)
Titre : Temporal and Spatial Evolution of the Interplanetary Medium
Quand : Mercredi 10 Février, 11h
Lieu : salle de l’ex LIX (LPP-Palaiseau)
Résumé :
The interplanetary medium is composed of two main populations : the solar wind plasma and the interplanetary dust, and both make in equal parts the large majority of the mass flux in the Solar System. Measuring and interpreting correctly the plasma and dust particles, using both ground and space-based instruments, are essential to understand the properties of plasmas in non-local thermodynamic equilibrium and their interaction with solar system bodies. It is in this context that I studied kinetic physics of the corona and solar wind and developed new techniques to detect interplanetary dust.

I will present observation of the large scale properties of the solar wind and solar corona and their evolution with the solar activity. I will show trends in the energy flux of the solar wind using observations from the Helios, Ulysses, and Wind spacecraft, showing an unexpected consistency in the energy flux of the solar wind at any given time, across very different source regions on the solar surface. I will also present new measurements of the radial profile of electron temperature using an improved analysis of the quasi-thermal noise on the Ulysses spacecraft, and how this measurement method applied to the upcoming Solar orbiter and Solar Probe Plus radio instruments will have significant implications for understanding the heating mechanisms active in the solar wind.

Finally, I will discuss recent work that shows the ability of electric field antennas to indirectly characterize dust of a few manometer (so called nanodust) by detecting the expanding plasma produced when a high-speed dust grain impacts the spacecraft. I showed that the power spectrum of the electric field measured by the STEREO/WAVES Low Frequency Receiver can be used to characterize dust properties. By methodically applying my algorithm on the entire STEREO/WAVES Low Frequency Receiver data, I have been able for the first time to show the effect of magnetic clouds on the nanodust flux measured at 1 AU, and of the interaction of Mercury and Venus with the dust, leading to observable modification of the observed nanodust flux.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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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)