Imaging and spectroscopic observations of magnetic reconnection and chromospheric evaporation in a solar flare

Hui Tian, Gang Li, Katharine K. Reeves, John C. Raymond, Fan Guo, Wei Liu, Bin Chen, Nicholas A. Murphy

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

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-1 along the line of sight) Fe XXI 1354.08 Å emission line with a 100 km s-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-1 at the loop footpoints, where the cool lines mentioned above all exhibit obvious redshift, a result that is consistent with the scenario of chromospheric evaporation induced by downward-propagating nonthermal electrons from the reconnection site.

Original languageEnglish (US)
Article numberL14
JournalAstrophysical Journal Letters
Volume797
Issue number2
DOIs
StatePublished - Dec 20 2014
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Sun: chromosphere
  • Sun: flares
  • Sun: transition region
  • line: profiles
  • magnetic reconnection

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