The 3D geometry of active region upflows deduced from their limb-to-limb evolution

• Autores: Démoulin, Pascal; Baker, D.; Mandrini, Cristina Hemilse; van Driel Gesztelyi, Lidia
• Año de publicación: 2013
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Active Regions, Magnetic Fields; Active Regions, Velocity Fields; Corona, Active; Spectral Line, Broadening
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We analyze the evolution of coronal plasma upflows from the edges of AR 10978, which has the best limb-to-limb data coverage with Hinode’s EUV Imaging Spectrometer (EIS). We find that the observed evolution is largely due to the solar rotation progressively changing the viewpoint of nearly stationary flows. From the systematic changes in the upflow regions as a function of distance from disc center, we deduce their 3D geometrical properties as inclination and angular spread in three coronal lines (Si vii, Fe xii, and Fe xv). In agreement with magnetic extrapolations, we find that the flows are thin, fan-like structures rooted in quasi separatrix layers (QSLs). The fans are tilted away from the AR center. The highest plasma velocities in these three spectral lines have similar magnitudes and their heights increase with temperature. The spatial location and extent of the upflow regions in the Si vii, Fe xii, and Fe xv lines are different owing to i) temperature stratification and ii) line of sight integration of the spectral profiles with significantly different backgrounds. We conclude that we sample the same flows at different temperatures. Further, we find that the evolution of line widths during the disc passage is compatible with a broad range of velocities in the flows. Everything considered, our results are compatible with the AR upflows originating from reconnections along QSLs between over-pressure AR loops and neighboring under-pressure loops. The flows are driven along magnetic field lines by a pressure gradient in a stratified atmosphere. Our interpretation of the above results is that, at any given time, we observe the superposition of flows created by successive reconnections, leading to a broad velocity distribution.
Fil: Démoulin, Pascal. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia
Fil: Baker, D.. UCL-Mullard Space Science Laboratory; Reino Unido
Fil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: van Driel Gesztelyi, Lidia. Konkoly Observatory; Hungría