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Title: THE 2014 MARCH 29 X-FLARE: SUBARCSECOND RESOLUTION OBSERVATIONS OF Fe XXI λ1354.1

The Interface Region Imaging Spectrometer (IRIS) is the first solar instrument to observe ∼10 MK plasma at subarcsecond spatial resolution through imaging spectroscopy of the Fe XXI λ1354.1 forbidden line. IRIS observations of the X1 class flare that occurred on 2014 March 29 at 17:48 UT reveal Fe XXI emission from both the flare ribbons and the post-flare loop arcade. Fe XXI appears at all of the chromospheric ribbon sites, although typically with a delay of one raster (75 s) and sometimes offset by up to 1''. 100-200 km s{sup –1} blue-shifts are found at the brightest ribbons, suggesting hot plasma upflow into the corona. The Fe XXI ribbon emission is compact with a spatial extent of <2'', and can extend beyond the chromospheric ribbon locations. Examples are found of both decreasing and increasing blue-shift in the direction away from the ribbon locations, and blue-shifts were present for at least six minutes after the flare peak. The post-flare loop arcade, seen in Atmospheric Imaging Assembly 131 Å filtergram images that are dominated by Fe XXI, exhibited bright loop-tops with an asymmetric intensity distribution. The sizes of the loop-tops are resolved by IRIS at ≥1'', and line widths in the loop-tops are notmore » broader than in the loop-legs suggesting the loop-tops are not sites of enhanced turbulence. Line-of-sight speeds in the loop arcade are typically <10 km s{sup –1}, and mean non-thermal motions fall from 43 km s{sup –1} at the flare peak to 26 km s{sup –1} six minutes later. If the average velocity in the loop arcade is assumed to be at rest, then it implies a new reference wavelength for the Fe XXI line of 1354.106 ± 0.023 Å.« less
Authors:
 [1] ;  [2] ;  [3]
  1. College of Science, George Mason University, Fairfax, VA 22030 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  3. Department of Physics, Montana State University, P.O. Box 173840, Bozeman, MT 59717 (United States)
Publication Date:
OSTI Identifier:
22364304
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 799; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; CHROMOSPHERE; HOT PLASMA; IMAGES; INTERFACES; IRON IONS; LINE WIDTHS; MULTICHARGED IONS; SPATIAL RESOLUTION; STELLAR CORONAE; STELLAR FLARES; SUN; TURBULENCE; ULTRAVIOLET RADIATION; VELOCITY; WAVELENGTHS