Chromospheric Condensation and Quasi-periodic Pulsations in a Circular-ribbon Flare

Abstract

In this paper, we report our multiwavelength observations of the C3.1 circular-ribbon flare SOL2015-10-16T10:20 in AR 12434. The flare consisted of a circular flare ribbon (CFR), an inner flare ribbon (IFR) inside, and a pair of short parallel flare ribbons (PFRs). During the impulsive phase of the flare, "two-step" raster observations of \textit{IRIS} with a cadence of 6 s and an exposure time of 2 s show plasma downflow at the CFR in the Si {\sc iv} $\lambda$1402.77 line, suggesting chromospheric condensation. The downflow speeds first increased rapidly from a few km s${}^{-1}$ to the peak values of 45$-$52 km s${}^{-1}$, before decreasing gradually to the initial levels. The decay timescales of condensation were 3$-$4 minutes, indicating ongoing magnetic reconnection. Interestingly, the downflow speeds are positively correlated with logarithm of the Si {\sc iv} line intensity and time derivative of the \textit{GOES} soft X-ray (SXR) flux in 1$-$8 Å. The radio dynamic spectra are characterized by a type \Rmnum{3} radio burst associated with the flare, which implies that the chromospheric condensation was most probably driven by nonthermal electrons. Using an analytical expression and the peak Doppler velocity, we derived the lower limit of energy flux of the precipitating electrons, i.e., 0.65$\times$10${}^{10}$ erg cm${}^{-2}$ s${}^{-1}$. The Si {\sc iv} line intensity and SXR derivative show quasi-periodic pulsations with periods of 32$-$42 s.

41 pages, 13 figures, 2 tables. Accepted for publication in ApJ

References in corpus (11)

• The Solar Optical Telescope for the Hinode Mission: An Overview
• Temporal evolution of multiple evaporating ribbon sources in a solar flare
• Imaging and spectroscopic observations of magnetic reconnection and chromospheric evaporation in a solar flare
• Quasi-periodic Slipping Magnetic Reconnection During an X-class Solar Flare Observed by the Solar Dynamics Observatory and Interface Region Imaging Spectrograph
• The 2014 March 29 X-flare: sub-arcsecond resolution observations of Fe XXI 1354.1
• Spatially-Resolved Nonthermal Line Broadening During The Impulsive Phase of a Solar Flare
• Multiwavelength observations of a partially eruptive filament on 2011 September 8
• Microwave Quasi-periodic Pulsations in Multi-timescales Associated with a Solar Flare/CME Event
• Quasi-Periodic Pulsations during the Impulsive and Decay phases of an X-class Flare
• Evidence of Explosive Evaporation in a Microflare Observed by Hinode/EIS
• Radiation Hydrodynamics in Solar Flares

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