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Theses

Modélisation dynamique de la couronne et du vent solaire

Abstract : This thesis focuses on the numerical and theoretical study of the dynamical coupling between the photosphere, the corona and the solar wind in the frame of the time-dependant magneto-hydrodynamics. I attempt to characterise the effects of the photospheric movements over the corona and wind taking into account the propagation conditions through the atmospheric layers, which comprise strong magnetic and thermal gradients. I start by showing that shear between the photospheric footpoints of magnetic coronal loop which spans over several scale-heights vanishes in a timescale of the order of the alfvénic transit time. This result, which contradicts a standard hypothesis, motivated the adoption of transparent boundary conditions (as opposed to rigid) in what followed. I then study the response of multipolar structures with null points to alfvénic perturbations in an axisymmetrical isothermal corona and wind. Reconnection and current accumulation occur near the null points. Ohmic dissipation, stimulated by persistent flows which develop in the system, occurs in the limit of vanishing resistivity. One of the studied cases, in which an over-dense jet forms above a magnetic bipole, is proposed as a model for polar plumes. The cold chromospheric layers were finally introduced in an 1D wind model with an energy equation. This model allowed the study of the formation and decay of polar plumes by varying the heating rate over the low corona, offering an alternative viewpoint to the previous model
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Rui Pinto. Modélisation dynamique de la couronne et du vent solaire. Astrophysique stellaire et solaire [astro-ph.SR]. Observatoire de Paris, 2009. Français. ⟨tel-01958552⟩

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