A study of extreme ultraviolet spectral line broadening in solar flares
Solar and Stellar Flares: observation, theory and simulations
Natasha Jeffrey
Lyndsay Fletcher and Nicolas Labrosse (University of Glasgow)
University of Glasgow
Extreme ultraviolet (EUV) spectral line properties close to observed solar flare X-ray footpoints are studied using the Hinode EUV Imaging Spectrometer (EIS) and the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We study how EUV spectral line broadening changes with wavelength, time and position across and along the X-ray footpoints of flare SOL2013-05-15T01:14, an X1.2 class flare, located close to the eastern solar limb. Both spatially resolved and spatially integrated changes in line broadening are compared with changes in electron number density, line intensity and line centroid position. Since SOL2013-05-15T01:14 is located close to the solar limb, possible variations with height, are also examined. Although it is difficult to make definite conclusions regarding the spatially resolved observations, the highest levels of line broadening are observed close to the edges of ribbons, and the lowest close to the centre of the footpoint. A number of interesting trends are found from the spatially integrated observations: the greatest line broadening occurs for the hottest line (Fe XXIII), at the earliest observed footpoint time, at a position close to the footpoint centroid, and the highest levels of broadening for cooler lines (Fe XV, Fe XVI,Fe XII) appear progressively closer to the loop top, with the broadening of each line decreasing as time progresses. Increases in electron number density occur at positions further from the loop top source, at earlier times during the flare, and closer to the loop top position at later times. Processes producing such observations will be discussed.
16:30 - 18:00