Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010apj...719..213w&link_type=abstract
The Astrophysical Journal, Volume 719, Issue 1, pp. 213-219 (2010).
Astronomy and Astrophysics
Astronomy
3
Line: Profiles, Sun: Corona, Sun: Flares, Sun: Uv Radiation
Scientific paper
Explosive chromospheric evaporation is predicted from some current solar flare models. In this paper, we analyze a flare with high time cadence raster scans with the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft. This observation covers an area of 240'' × 240'', with the 1'' slit in about 160 s. The early phases of a C9.7 flare that occurred on 2007 June 6 were well observed. The purpose of our analysis is to study for the first time the spatially resolved spectra of high-temperature plasma, especially from Fe XXIII and Fe XXIV, allowing us to explore the explosive chromospheric evaporation scenario further. Sections of raster images obtained between 17:20:09 and 17:20:29 (UT) show a few bright patches of emission from Fe XXIII/Fe XXIV lines at the footpoints of the flaring loops; these footpoints were not clearly seen in the images taken earlier, between 17:17:30 and 17:17:49 (UT). Fe XXIII spectra at these footpoints show dominating blueshifted components of -(300 to 400) km s-1, while Fe XV/XIV lines are nearly stationary; Fe XII lines and/or lower temperature lines show slightly redshifted features, and Fe VIII and Si VII to He II lines show ~+50 km s-1 redshifted components. The density of the 1.5-2 MK plasma at these footpoints is estimated to be 3 × 1010 cm-3 by the Fe XIII/XIV line pairs around the maximum of the flare. High-temperature loops connecting the footpoints appear in the Fe XXIII/XXIV images taken over 17:22:49-17:23:08 (UT) which is near the flare peak. Line profiles of these high-temperature lines at this flare peak time show only slowly moving components. The concurrent cooler Fe XVII line at 254.8 Å is relatively weak, indicating the predominance of high-temperature plasma (>107 K) in these loops. The characteristics observed during the early phases of this flare are consistent with the scenario of explosive chromospheric evaporation.
Hara Hirohisa
Harra Louise K.
Sterling Alphonse C.
Watanabe Tetsuya
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