Dynamique turbulente de la couronne et du vent solaires

Abstract : The variability of the heliosphere and in particular ``space weather'' are the result of a chain of processes involving the solar corona and wind. Turbulence plays a fundamental role in these phenomena, but it makes them (as well as their stellar analogues) very complex, with a wide range of scales and a large number of physical mechanisms. The corona can thus be heated to more than a million kelvins by the dissipation of small-scale structures that are created by turbulence. Observations allowed us to investigate properties of turbulence and heating events, and the thermal structure of the transition region between the thereby heated corona and the cooler lower layers of the solar atmosphere. I have modeled turbulent heating in the case of magnetically closed (coronal loops) and open (coronal holes) regions. In coronal loops, I have demonstrated the existence of a feedback between heating and cooling processes, and I have obtained signatures of turbulent heating. In coronal holes, we have shown that this heating could accelerate the wind, and we have also obtained spectra of anisotropic MHD and Hall-MHD turbulence. At the interface between both these types of coronal regions, we have determined the proportion of the mass flux in a coronal jet that effectively contributes to the wind. The magnetic field also maintains filaments of cool material in the hot corona, and their eruption can strongly disturb the heliosphere; we have observed one of these eruptions in detail, and we are developing a code to detect these structures automatically, before their eruption.
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Submitted on : Tuesday, September 8, 2015 - 1:39:28 PM
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Eric Buchlin. Dynamique turbulente de la couronne et du vent solaires. Astrophysique stellaire et solaire [astro-ph.SR]. Paris-Sud XI, 2014. ⟨tel-01195751⟩

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