Ashok Kumar Baral | Searcharxiv

arXiv2026

Kinematics and Untwisting Motion of an Intriguing Jet-like Prominence Eruption

We aim to investigate the blowout jet-like prominence eruption, which occurred on October 6$^{th}$, 2023, with the help of imaging and spectroscopic observations. Firstly, the prominence rises slowly with a speed of 33 km/s, followed by a fast rise (i.e., 338 km/s). Later, the northern leg breaks completely, and the eruption forms the blowout jet. The jet consists of different plasma threads, which show a range of upflow (i.e., 125 to 593 km/s) and downflow velocities (i.e., 43 to 158 km/s). The jet plasma column exhibits transverse oscillations, and this motion (untwisting motion) propagate at the speed of 267 km/s, are consistent with being Alfev{é}n waves. The transverse motion has the time period, amplitude, and transverse velocity of 1332 s, 26.19 Mm, and 126.18$\pm$7.27 km/s, respectively, and this transverse oscillation decays over time. Interestingly, the different plasma threads within the jet's body exhibit decayless transverse oscillations, and these decayless oscillations are related to the main decaying transverse oscillation. The transverse velocity of these decayless oscillations ranges from 66 to 30 km/s, the amplitudes from 8.52 to 2.74 Mm, and periods from 811 to 406 s. In addition, the spectroscopic analysis reveals Si~{\sc iv} lines are forming in the optically thick conditions in high electron density regions (i.e., near the base of the blowout jet). Lastly, we mention that two weak C-class flares occurred during this event, and further, one CME also occurred, which propagated with the speed of $\sim$250 km/s.

astro-ph.SR↗

arXiv2026

Sigmoid Formation, Filament Destabilization, and Initiation of Weak Flare by Tether-Cutting Reconnection

We have studied a B-class solar flare and an associated filament eruption through multi-wavelength observations. The flare triggers at 16:24~UT on June 7$^{th}$, 2017 from an active region (AR) 12661, and it maximizes at 16:54~UT. The magnetic flux cancellation occurs near the polarity inversion line (PIL) preceding the flare, and ultraviolet (UV) brightenings occur in the pre-flare phase at the flux cancellation sites, suggesting the reconnection occurs in the lower atmosphere, initially. The S-shaped sigmoid forms through successive steps in corona, i.e., small-scale brightenings, helical/twisted field lines, bright patches, and finally, a developed sigmoid. It justifies that runaway reconnection within the coronal arcades forms the sigmoid within the filament. The differential emission-measure (DEM) analysis reveals the existence of the plasma at a temperature of more than 10 MK within the sigmoid. The initial magnetic reconnection reorganizes the field overlying the filament as per the tether-cutting model. Therefore, it enables the filament to rise slowly, and around~16:41~UT, the eruption phase of the filament begins. The filament eruption removes the overlying coronal field, including the sigmoid. During the eruption phase, we have found intersecting/crossing of coronal loops and jet-like structures far away from the sigmoid-filament system. In conclusion, all the observational findings (e.g., magnetic flux convergence, cancellation, UV brightenings, and spatial and temporal correlation between formation/evolution of the sigmoid and rise/eruption of the filament) suggest that the formation of a solar flare and the eruption of the filament are consistent with the tether-cutting model of solar eruption.

astro-ph.SR↗