E-Print Archive

There are 3991 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Chromospheric Condensation and Quasi-periodic Pulsations in a Circular-ribbon Flare View all abstracts by submitter

Qingmin Zhang   Submitted: 2016-09-13 02:44

In 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, and a pair of short parallel flare ribbons (PFRs). The PFRs located to the north of IFR were most striking in the Interface Region Imaging Spectrograph (IRIS) 1400 Å and 2796 Å images. For the first time, we observed the circular-ribbon flare in the Ca II H line of the Solar Optical Telescope (SOT) aboard Hinode, which has similar shape as observed in the Atmospheric Imaging Assembly (AIA) 1600 Å aboard the Solar Dynamic Observatory (SDO). Photospheric line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) aboard SDO show that the flare was associated with positive polarities and 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 the 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 show plasma downflow at the CFR in the Si IV \lambda1402.77 line (log T≈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 logarithm of the Si IV line intensity and time derivative of the GOES soft X-ray (SXR) flux in 1-8 Å. 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 derived the lower limit of energy flux of the precipitating electrons, i.e., 0.65x1010 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.

Authors: Q. M. Zhang, D. Li, and Z. J. Ning
Projects: IRIS

Publication Status: accepted for publication in ApJ
Last Modified: 2016-09-14 12:01
Go to main E-Print page  Evolution of the Magnetic Field Distribution of Active Regions  Helical Kink Instability in a Confined Solar Eruption  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Key
Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
Investigation of pre-flare dynamics using the weighted horizontal magnetic gradient method: From small to major flare classes
Seismological determination of the Alfvén speed and plasma-beta in solar photospheric bright points
Dynamo Wave Patterns Inside the Sun Revealed by Torsional Oscillations
Evidence of Twisting and Mixed-polarity Solar Photospheric Magnetic Field in Large Penumbral Jets: IRIS and Hinode Observations
Dissipation scale lengths of density turbulence in the inner solar wind
On the Possibility of Generating Harmonics of the Electron Plasma Frequency in the Solar Atmosphere due to Explosive Instability in a System of Interpenetrating Electron and Ion Flows
Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra
Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
Can high-mode magnetohydrodynamic waves propagating in a spinning macrospicule be unstable due to the Kelvin-Helmholtz instability?
The development of lower-atmosphere turbulence early in a solar flare
Determining the parameter for the linear force-free magnetic field model with multi-dipolar configurations using deep neural networks
No unique solution to the seismological problem of standing kink MHD waves
Untwisting and Disintegration of a Solar Filament Associated with Photospheric Flux Cancellation
Modeling of the sunspot-associated microwave emission using a new method of DEM inversion
Energy transport and heating by torsional Alfvén waves propagating from the photosphere to the corona in the quiet Sun
A Two-Step Magnetic Reconnection in a Confined X-class Flare in Solar Active Region 12673
Lifetimes and Emergence/Decay Rates of Star Spots on Solar-type Stars Estimated by Kepler Data in Comparison with Those of Sunspots
IRIS and SDO Observations of Solar Jetlets Resulting from Network-edge Flux Cancelation
Si IV Resonance Line Emission During Solar Flares: Non-LTE, Non-equilibrium, Radiation Transfer Simulations
Study of current sheets in the wake of two crossing filaments eruption

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University