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

We aim to investigate the blowout jet-like prominence eruption, which occurred on 2023 October 6, with the help of imaging and spectroscopic observations. Firstly, the prominence rises slowly at a speed of 33 km s⁻¹, followed by a fast rise (i.e., 338 km s⁻¹). 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., 125–593 km s⁻¹) and downflow velocities (i.e., 43–158 km s⁻¹). The jet plasma column exhibits transverse oscillations, and this motion (untwisting motion) propagates at a speed of 267 km s⁻¹. This transverse motion is consistent with being Alfvén waves. The transverse motion has a time period, amplitude, and transverse velocity of 1332 s, 26.19 Mm, and 126.18 ± 7.27 km s⁻¹, 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⁻¹, the amplitudes from 8.52 to 2.74 Mm, and periods from 811 to 406 s. In addition, the spectroscopic analysis reveals that Si iv lines are forming under 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 coronal mass ejection also occurred, which propagated at a speed of ∼250 km s⁻¹.