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CHROMOSPHERIC CONDENSATION AND QUASI-PERIODIC PULSATIONS IN A CIRCULAR-RIBBON FLARE
Zhang, Q. M.1,2; Li, D.1; Ning, Z. J.1
2016-11-20
Source PublicationASTROPHYSICAL JOURNAL
ISSN0004-637X
Volume832Issue:1Pages:16
Corresponding AuthorZhang, Q. M.(zhangqm@pmo.ac.cn)
AbstractIn this paper, we report our multiwavelength observations of the C3.1 circular-ribbon flare SOL2015-10-16T10: 20 in active region (AR) 12434. The flare consisted of a circular flare ribbon (CFR), an inner flare ribbon (IFR) inside it, and a pair of short parallel flare ribbons (PFRs). The PFRs located to the north of the IFR were most striking in the Interface Region Imaging Spectrograph (IRIS) 1400 and 2796 angstrom images. For the first time, we observed the circular-ribbon flare in the Ca II H line of the Solar Optical Telescope on board Hinode, which has a similar shape as observed in the Atmospheric Imaging Assembly 1600 angstrom on board the Solar Dynamic Observatory (SDO). Photospheric line-of-sight magnetograms from the Helioseismic and Magnetic Imager on board SDO show that the flare is associated with positive polarities with a negative polarity inside. The IFR and CFR were cospatial with the negative polarity and positive polarities, implying the existence of a magnetic null point (B = 0) and a dome-like spine-fan topology. During the impulsive phase of the flare, " two-step" raster observations of IRIS with a cadence of 6 s and an exposure time of 2 s showed plasma downflow at the CFR in the Si IV.1402.77 line (log T approximate to 4.8), suggesting chromospheric condensation. The downflow speeds first increased rapidly from a few km s(-1) to the peak values of 45-52 km s(-1), before decreasing gradually to the initial levels. The decay timescales of condensation were 3-4 minutes, indicating ongoing magnetic reconnection. Interestingly, the downflow speeds are positively correlated with the logarithm of the Si IV line intensity and time derivative of the GOES soft X-ray (SXR) flux in 1-8 angstrom. The radio dynamic spectra are characterized by a type III radio burst associated with the flare, which implies that the chromospheric condensation was most probably driven by nonthermal electrons. Using an analytical expression and the peak Doppler velocity, we derive the lower limit of energy flux of the precipitating electrons, i.e., 0.65 x 10(10) erg cm(-2) s(-1). The Si IV line intensity and SXR derivative show quasi-periodic pulsations with periods of 32-42 s, which are likely caused by intermittent null-point magnetic reconnections modulated by the fast wave propagating along the fan surface loops at a phase speed of 950-1250 km s(-1). Periodic accelerations and precipitations of the electrons result in periodic heating observed in the Si IV line and SXR.
KeywordSun: chromosphere Sun: corona Sun: flares Sun: X-rays, gamma rays techniques: spectroscopic
DOI10.3847/0004-637X/832/1/65
WOS KeywordLOOP RADIATIVE HYDRODYNAMICS ; REGION-IMAGING-SPECTROGRAPH ; SLOW MAGNETOACOUSTIC WAVES ; CLASS SOLAR-FLARE ; MAGNETIC RECONNECTION ; EXTREME-ULTRAVIOLET ; ELECTRON-BEAMS ; MULTIWAVELENGTH OBSERVATIONS ; NONTHERMAL ELECTRONS ; RAY-EMISSION
Indexed BySCI
Language英语
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000391453400001
PublisherIOP PUBLISHING LTD
Citation statistics
Document Type期刊论文
Identifierhttp://libir.pmo.ac.cn/handle/332002/22854
Collection中国科学院紫金山天文台
Corresponding AuthorZhang, Q. M.
Affiliation1.Chinese Acad Sci, Purple Mt Observ, Key Lab Dark Matter & Space Sci, Nanjing 210008, Jiangsu, Peoples R China
2.Chinese Acad Sci, Natl Astron Observ, Key Lab Solar Act, Beijing 100012, Peoples R China
Recommended Citation
GB/T 7714
Zhang, Q. M.,Li, D.,Ning, Z. J.. CHROMOSPHERIC CONDENSATION AND QUASI-PERIODIC PULSATIONS IN A CIRCULAR-RIBBON FLARE[J]. ASTROPHYSICAL JOURNAL,2016,832(1):16.
APA Zhang, Q. M.,Li, D.,&Ning, Z. J..(2016).CHROMOSPHERIC CONDENSATION AND QUASI-PERIODIC PULSATIONS IN A CIRCULAR-RIBBON FLARE.ASTROPHYSICAL JOURNAL,832(1),16.
MLA Zhang, Q. M.,et al."CHROMOSPHERIC CONDENSATION AND QUASI-PERIODIC PULSATIONS IN A CIRCULAR-RIBBON FLARE".ASTROPHYSICAL JOURNAL 832.1(2016):16.
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