Explosive chromospheric evaporation in a circular-ribbon flare

Journal Article · Wed Aug 10 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/827/1/27· OSTI ID:22868814

Zhang, Q. M.; Li, D.; Ning, Z. J.; Su, Y. N.; Ji, H. S. ^[1]

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1. Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, CAS, Nanjing 210008 (China)

In this paper, we report our multiwavelength observations of the C4.2 circular-ribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such a magnetic pattern is strongly indicative of a magnetic null point and spine-fan configuration in the corona. The flare was triggered by the eruption of a mini-filament residing in the AR, which produced the inner flare ribbon (IFR) and the southern part of a closed circular flare ribbon (CFR). When the eruptive filament reached the null point, it triggered null point magnetic reconnection with the ambient open field and generated the bright CFR and a blowout jet. Raster observations of the Interface Region Imaging Spectrograph show plasma upflow at speeds of 35–120 km s{sup −1} in the Fe xxi λ1354.09 line (logT≈7.05) and downflow at speeds of 10–60 km s{sup −1} in the Si iv λ1393.77 line (logT≈4.8) at certain locations of the CFR and IFR during the impulsive phase of the flare, indicating explosive chromospheric evaporation. Coincidence of the single hard X-ray source at 12–25 keV with the IFR and calculation based on the thick-target model suggest that the explosive evaporation was most probably driven by nonthermal electrons.

• OSTI ID: 22868814
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 827; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CHROMOSPHERE
COSMIC ELECTRONS
EVAPORATION
GAMMA RADIATION
HARD X RADIATION
MAGNETIC RECONNECTION
PLASMA
SOLAR CORONA
SOLAR FLARES
SUN
VELOCITY
X-RAY SOURCES