Microwave Study of a Solar Circular Ribbon Flare
arXiv:2009.11926 · doi:10.3847/2041-8213/abb4dd
Abstract
A circular ribbon flare SOL2014-12-17T04:51 is studied using the 17/34 GHz maps from the Nobeyama Radioheliograph (NoRH) along with (E)UV and magnetic data from the Solar Dynamics Observatory (SDO). We report the following three findings as important features of the microwave CRF. (1) The first preflare activation comes in the form of a gradual increase of the 17 GHz flux without a counterpart at 34 GHz, which indicates thermal preheating. The first sign of nonthermal activity occurs in the form of stepwise flux increases at both 17 and 34 GHz about 4 min before the impulsive phase. (2) Until the impulsive phase, the microwave emission over the entire active region is in a single polarization state matching the magnetic polarity of the surrounding fields. During and after the impulsive phase, the sign of the 17 GHz polarization state reverses in the core region, which implies a magnetic breakout--type eruption in a fan-spine magnetic structure. (3) The 17 GHz flux around the time of the eruption shows quasi-periodic variations with periods of 1--2 min. The pre-eruption oscillation is more obvious in total intensity at one end of the flare loop, and the post-eruption oscillation, more obvious in the polarized intensity at a region near the inner spine. We interpret this transition as the transfer of oscillatory power from kink mode oscillation to torsional Alfvén waves propagating along the spine field after the eruption. We argue that these three processes are inter-related and indicate a breakout process in a fan-spine structure.
References in corpus (19)
- Hot Spine Loops and the Nature of a Late-Phase Solar Flare
- Circular Ribbon Flares and Homologous Jets
- Fan-spine topology formation through two-step reconnection driven by twisted flux emergence
- A Breakout Model for Solar Coronal Jets with Filaments
- Current amplification and magnetic reconnection at a 3D null point. I - Physical characteristics
- On the nature of reconnection at a solar coronal null point above a separatrix dome
- Current sheet formation and non-ideal behaviour at three-dimensional magnetic null points
- Three-Dimensional Simulations of Tearing and Intermittency in Coronal Jets
- X-ray and UV investigation into the magnetic connectivity of a solar flare
- A model for straight and helical solar jets: II. Parametric study of the plasma beta
- Reconnection-Driven Coronal-Hole Jets with Gravity and Solar Wind
- Evidence for Solar Tether-cutting Magnetic Reconnection from Coronal Field Extrapolations
- Flux rope, hyperbolic flux tube, and late EUV phases in a non-eruptive circular-ribbon flare
- Record-breaking coronal magnetic field in solar active region 12673
- Reconnection Properties of Large-Scale Current Sheets During Coronal Mass Ejection Eruptions
- Transverse coronal loop oscillations excited by homologous circular-ribbon flares
- Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
- Two-stage energy release process of a confined flare with double HXR peaks
- Heating and Eruption of a Solar Circular Ribbon Flare