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SUMMARY:How heavy is a shadow? - Dr. David Williams (MSSL\, UCL)
DTSTART:20140610T120000Z
DTEND:20140610T130000Z
UID:TALK50838@talks.cam.ac.uk
CONTACT:Dr. Jaroslav Dudik
DESCRIPTION:The thin wisps of reddish gas observed peeking out above an ec
 lipsed Sun are prominences\, known as filaments when observed on the solar
  disc. These structures contain large amounts of neutral hydrogen (hence t
 heir reddish colour) and helium\, and in recent decades\, we have come to 
 understand that they are often the important dense core of a coronal mass 
 ejection. CMEs are violent eruptions of magnetically confined and driven p
 lasma that are flung into the solar system\, with sometimes very disruptiv
 e consequences at Earth.\n\nOn 7th June 2011\, one such eruption captured 
 the attention of solar physicists because – unusually – much of the ma
 terial inside the erupting filament cascaded back towards the Sun. In atte
 mpting to understand why this should be the case\, we developed a method f
 or measuring the density of hydrogen in the ejecta\, using state-of-the-ar
 t multi-wavelength imaging data. The superior time resolution\, sensitivit
 y and near-synchronicity of data from the Solar Dynamics Observatory's ext
 reme UV cameras allow us to combine these two techniques using photo-ionis
 ation continuum opacity to determine the spatial distribution of hydrogen 
 in filament material. We present our results from this study\, and specula
 te on why this spectacular eruption was so unusual\, and what the techniqu
 e offers for the future of filament studies.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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