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Title: IMAGING AND SPECTROSCOPIC OBSERVATIONS OF MAGNETIC RECONNECTION AND CHROMOSPHERIC EVAPORATION IN A SOLAR FLARE

Magnetic reconnection is believed to be the dominant energy release mechanism in solar flares. The standard flare model predicts both downward and upward outflow plasmas with speeds close to the coronal Alfvén speed. Yet, spectroscopic observations of such outflows, especially the downflows, are extremely rare. With observations of the newly launched Interface Region Imaging Spectrograph (IRIS), we report the detection of a greatly redshifted (∼125 km s{sup –1} along the line of sight) Fe XXI 1354.08 Å emission line with a ∼100 km s{sup –1} nonthermal width at the reconnection site of a flare. The redshifted Fe XXI feature coincides spatially with the loop-top X-ray source observed by RHESSI. We interpret this large redshift as the signature of downward-moving reconnection outflow/hot retracting loops. Imaging observations from both IRIS and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory also reveal the eruption and reconnection processes. Fast downward-propagating blobs along these loops are also found from cool emission lines (e.g., Si IV, O IV, C II, Mg II) and images of AIA and IRIS. Furthermore, the entire Fe XXI line is blueshifted by ∼260 km s{sup –1} at the loop footpoints, where the cool lines mentioned above all exhibitmore » obvious redshift, a result that is consistent with the scenario of chromospheric evaporation induced by downward-propagating nonthermal electrons from the reconnection site.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  2. Department of Physics and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
  3. Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States)
  4. Lockheed Martin Solar and Astrophysics Laboratory, Building 252, 3251 Hanover Street, Palo Alto, CA 94305 (United States)
Publication Date:
OSTI Identifier:
22364868
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 797; 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; CHROMOSPHERE; DETECTION; ERUPTION; EVAPORATION; IMAGES; INTERFACES; IRON IONS; MAGNETIC RECONNECTION; PLASMA; RED SHIFT; SOLAR ELECTRONS; SOLAR FLARES; STAR MODELS; SUN; X-RAY SOURCES