PRODUCTION OF HIGH-TEMPERATURE PLASMAS DURING THE EARLY PHASES OF A C9.7 FLARE

Journal Article · Tue Aug 10 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/719/1/213· OSTI ID:21455023

Watanabe, Tetsuya; Hara, Hirohisa ^[1]; Sterling, Alphonse C ^[2]

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1. National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
2. MSFC, NASA, Huntsville, AL 35812 (United States)

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'' x 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{sup -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 {approx}+50 km s{sup -1} redshifted components. The density of the 1.5-2 MK plasma at these footpoints is estimated to be 3 x 10{sup 10} cm{sup -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 A is relatively weak, indicating the predominance of high-temperature plasma (>10{sup 7} K) in these loops. The characteristics observed during the early phases of this flare are consistent with the scenario of explosive chromospheric evaporation.

• OSTI ID: 21455023
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 719; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ATMOSPHERES
ELECTROMAGNETIC RADIATION
HOT PLASMA
MAIN SEQUENCE STARS
MEASURING INSTRUMENTS
PLASMA
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR CORONA
SOLAR FLARES
SPECTROMETERS
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR FLARES
SUN
ULTRAVIOLET RADIATION