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Evolutionary stages and triggering process of a complex eruptive flare with circular and parallel ribbons  

Navin Chandra Joshi   Submitted: 2021-01-30 23:56

We report multiwavelength study of a complex M-class solar eruptive flare that consists of three different sets of flare ribbons, viz. circular, parallel, and remote ribbons. Magnetic field modelling of source active region NOAA 12242 exhibits the presence of 3D null-point magnetic topology that encompasses an inner bipolar region. The event initiates with the faint signatures of the circular ribbon along with remote brightening right from the pre-flare phase that points toward the ongoing slow yet persistent null-point reconnection. We first detected flux cancellation and an associated brightening, which are likely signatures of tethercutting reconnection that builds the flux rope near the polarity inversion line (PIL) of the inner bipolar region. In the next stage, with the onset of M8.7 flare, there is a substantial enhancement in the brightening of circular ribbon, which essentially suggests an increase in the rate of ongoing null-point reconnection. Finally, the eruption of underlying flux rope triggers ‘standard flare reconnection’ beneath it producing an abrupt rise in the intensity of the parallel ribbons as well as enhancing the rate of null-point reconnection by external forcing. We show that within the the fan dome, the region with magnetic decay index n > 1.5 borders the null-point QSL. Our analysis suggests that both the torus instability and the breakout model have played role toward the triggering mechanism for the eruptive flare. This event is a nice example of the dynamical evolution of a flux rope initially confined in a null-point topology that subsequently activates and erupts with the progression of the circular-cum-parallel ribbon flare.

Authors: Navin Chandra Joshi, Bhuwan Joshi, Prabir K. Mitra
Projects: None,GOES X-rays,RHESSI,SDO-AIA,SDO-HMI,SoHO-LASCO

Publication Status: Published in MNRAS journal
Last Modified: 2021-02-01 15:55
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Sequential Lid Removal in a Triple-decker Chain of CME-producing Solar Eruptions  

Navin Chandra Joshi   Submitted: 2021-01-30 23:01

We investigate the onsets of three consecutive coronal mass ejection (CME) eruptions in 12 hr from a large bipolar active region (AR) observed by the Solar Dynamics Observatory (SDO), the Solar Terrestrial Relations Observatory (STEREO), the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and the Geostationary Operational Environmental Satellite (GOES). Evidently, the AR initially had a “triple-decker” configuration: three flux ropes in a vertical stack above the polarity inversion line (PIL). Upon being bumped by a confined eruption of the middle flux rope, the top flux rope erupts to make the first CME and its accompanying AR-spanning flare arcade rooted in a far apart pair of flare ribbons. The second CME is made by eruption of the previously arrested middle flux rope, which blows open the flare arcade of the first CME and produces a flare arcade rooted in a pair of flare ribbons closer to the PIL than those of the first CME. The third CME is made by blowout eruption of the bottom flux rope, which blows open the second flare arcade and makes its own flare arcade and pair of flare ribbons. Flux cancellation observed at the PIL likely triggers the initial confined eruption of the middle flux rope. That confined eruption evidently triggers the first CME eruption. The lid-removal mechanism instigated by the first CME eruption plausibly triggers the second CME eruption. Further lid removal by the second CME eruption plausibly triggers the final CME eruption.

Authors: Navin Chandra Joshi, Alphonse C. Sterling, Ronald L. Moore, Bhuwan Joshi
Projects: GOES X-rays,RHESSI,SDO-AIA,SDO-HMI,SoHO-LASCO

Publication Status: Published in ApJ journal
Last Modified: 2021-02-01 15:55
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Sequential Lid Removal in a Triple-Decker Chain of CME-Producing Solar Eruptions  

Navin Chandra Joshi   Submitted: 2020-08-15 22:16

We investigate the onsets of three consecutive coronal mass ejection (CME) eruptions in 12 hours from a large bipolar active region (AR) observed by SDO, STEREO, RHESSI, and GOES. Evidently, the AR initially had a “triple–decker” configuration: three flux ropes in a vertical stack above the polarity inversion line (PIL). Upon being bumped by a confined eruption of the middle flux rope, the top flux rope erupts to make the first CME and its accompanying AR–spanning flare arcade rooted in a far-apart pair of flare ribbons. The second CME is made by eruption of the previously-arrested middle flux rope, which blows open the flare arcade of the first CME and produces a flare arcade rooted in a pair of flare ribbons closer to the PIL than those of the first CME. The third CME is made by blowout eruption of the bottom flux rope, which blows open the second flare arcade and makes its own flare arcade and pair of flare ribbons. Flux cancellation observed at the PIL likely triggers the initial confined eruption of the middle flux rope. That confined eruption evidently triggers the first CME eruption. The lid-removal mechanism instigated by the first CME eruption plausibly triggers the second CME eruption. Further lid removal by the second CME eruption plausibly triggers the final CME eruption.

Authors: Navin Chandra Joshi, Alphonse C. Sterling, Ronald L. Moore, Bhuwan Joshi
Projects: GOES X-rays,SDO-AIA,SDO-HMI,SoHO-LASCO,STEREO

Publication Status: Accepted for publication in ApJ
Last Modified: 2020-08-19 13:18
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Chain Reconnections observed in Sympathetic Eruptions  

Navin Chandra Joshi   Submitted: 2016-02-25 21:22

The nature of various plausible causal links between sympathetic events is still a controversial issue. In this work, we present multi-wavelength observations of sympathetic eruptions, associated flares and coronal mass ejections (CMEs) occurring on 2013 November 17 in two close-by active regions. Two filaments i.e., F1 and F2 are observed in between the active regions. Successive magnetic reconnections, caused by different reasons (flux cancellation, shear and expansion) have been identified during the whole event. The first reconnection occurred during the first eruption via flux cancellation between the sheared arcades overlying filament F2, creating a flux rope and leading to the first double ribbon solar flare. During this phase we observed the eruption of overlaying arcades and coronal loops, which leads to the first CME. The second reconnection is believed to occur between the expanding flux rope of F2 and the overlying arcades of the filament F1. We suggest that this reconnection destabilized the equilibrium of filament F1, which further facilitated its eruption. The third stage of reconnection occurred in the wake of the erupting filament F1 between the legs of overlying arcades. This may create a flux rope and the second double ribbon flare and a second CME. The fourth reconnection was between the expanding arcades of the erupting filament F1 and the nearby ambient field, which produced the bi-directional plasma flows towards both upward and downward. Observations and a nonlinear force-free field extrapolation confirm the possibility of reconnection and the causal link between the magnetic systems.

Authors: Navin Chandra Joshi, Brigitte Schmieder, Tetsuya Magara, Yang Guo, Guillaume Aulanier
Projects: GOES Particles,GONG,RHESSI,SDO-AIA,SDO-HMI,SoHO-LASCO,STEREO

Publication Status: Accepted for publication in ApJ
Last Modified: 2016-02-29 10:55
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Abstracts by Author
Evolutionary stages and triggering process of a complex eruptive flare with circular and parallel ribbons
Sequential Lid Removal in a Triple-decker Chain of CME-producing Solar Eruptions
Sequential Lid Removal in a Triple-Decker Chain of CME-Producing Solar Eruptions
Chain Reconnections observed in Sympathetic Eruptions

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