Yuandeng Shen

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 .

Remote brightening (RB) refers to brightening at a footpoint of magnetic loops in the solar atmosphere, which is passively triggered by an eruption occurring at the other footpoint. Here, we present observations of an RB event driven by an extreme-ultraviolet (EUV) jet. The leading front of the jet exhibits flows exceeding the characteristic sound speed, and it triggers RBs at two remote sites that are connected by coronal loops. We focus on the RB that occurred at one of the footpoints, in which the magnetic structure is characterized by a dome-like feature with magnetic null points. When the jet propagates to this footpoint, the brightening displays a distinct inverted-Y-shaped structure. Bidirectional flows with a velocity of about 30 km s ⁻¹ are detected in any two branches of this structure, which are suggestive of the occurrence of magnetic reconnection at this footpoint. To investigate the physics of the interaction between the jet and the remote magnetic null point, we conducted a 2D MHD simulation with adaptive mesh refinement. We find that the collapse of the magnetic null point is induced by a fast-mode wave, and the flow associated with the jet elongates the current sheet, thereby triggering plasmoid instability. Subsequent magnetic reconnection not only forms the bright inverted-Y-shaped structure but also drives bidirectional flows along the structures, being consistent with the observational findings. This study provides new insights into the dynamic interaction between EUV jets and remote magnetic nulls in the solar atmosphere, and helps understand the diverse natures of RBs.

Solar prominences (or filaments) are cooler and denser plasma suspended in the much hotter and rarefied solar corona. When viewed on the solar disk, filament barbs or feet protrude laterally from the filament spine. When observed at the limb of the Sun, they reach into the chromosphere or even further down. For a long time, the magnetic field orientation of barbs has remained a mystery due to the paradox that the barbs possess vertical fine structures and flows but are likely to be supported in a horizontal magnetic field. Here we present unambiguous observations of a magnetic dip in a quiescent prominence foot with an upward-curved field. That is indicated by the horizontal bidirectional outflows probably produced by magnetic reconnection between the fields of a tiny erupting filament and those in a prominence foot. The altitude at the bottom of the dip is ∼30 Mm. At the edge of the prominence foot, the angle between the dip field and the local horizontal is ∼4°. Additionally, the curvature radius of the dip bottom is estimated to be around 73 Mm. We also conduct magnetofrictional simulation to self-consistently form a large-scale magnetic flux rope with magnetic dips resembling the spine and feet of the quiescent prominence. The observations shed light on the field structure of prominences, which is crucial for the instability that accounts for the eruption of prominences and coronal mass ejections.

Solar jets are collimated plasma ejections driven by magnetic reconnection, which play a critical role in the energy release and mass transport in the solar atmosphere. Using Solar Orbiter’s Extreme Ultraviolet Imager (EUI) with its unprecedented spatiotemporal resolution, we report the discovery of nine transient coronal jets associated with a filament eruption on September 30, 2024. These jets, with a median lifetime of only 22 seconds, have significantly shorter timescales than previously observed coronal jets. They exhibit diverse morphologies and properties, evolving through three distinct phases of the filament eruption: initiation, rise, and peak. The spatial and temporal distribution of the jets suggests they are driven by dynamic magnetic reconnection between the erupting filament and overlying magnetic fields. These jets represent a distinct class of phenomena different from traditional mini-filament-driven jets, being directly associated with large-scale filament eruption processes. This study reveals a previously unrecognised class of highly transient jets, highlighting the complexity of reconnection-driven processes during filament eruptions and underscoring the importance of high-resolution observations in uncovering fundamental plasma dynamics in the solar atmosphere.

Solar filament eruptions play a key role in driving space weather, yet their fine-scale evolution remains poorly understood due to observational limitations. Using unprecedented high-resolution observations from Solar Orbiter’s Extreme Ultraviolet Imager (105 km/pixel) and Polarimetric and Helioseismic Imager, we detect persistent magnetic reconnection events in a failed filament eruption. We identify magnetic reconnections between the filament and the surrounding magnetic field structures, with a higher frequency and a greater variety of types than previously observed. These reconnections significantly affect the filament stability and eruption dynamics, leading to sequential coronal jets and failed eruptions. We propose a “persistent magnetic cutting” concept, highlighting how persistent small-scale magnetic reconnections cumulatively affect filament stability during its evolution.

Solar prominences (or filaments) are cooler and denser plasma suspended in the much hotter and rarefied solar corona. When viewed on the solar disc filament barbs or feet protrude laterally from filament spine. When observed at the limb of the Sun, they reach into the chromosphere or even further down. For a long time, the magnetic field orientation of barbs has remained a mystery due to the paradox that the barbs possess vertical fine structures and flows but are likely to be supported in a horizontal magnetic field. Here we present unambiguous observations of a magnetic dip in a quiescent prominence foot with an upward-curved field. That is indicated by the horizontal bidirectional outflows probably produced by magnetic reconnection between the fields of a tiny erupting filament and those in a prominence foot. The altitude at the bottom of the dip is about 30 Mm. At the edge of the prominence foot, the angle between the dip field and the local horizontal is about 4 degrees. Additionally, the curvature radius of the dip bottom is estimated to be around 73 Mm. We also conduct magnetofrictional simulation to self-consistently form a large-scale magnetic flux rope with magnetic dips resembling the spine and feet of the quiescent prominence. The observations shed light on the field structure of prominences which is crucial for the instability that accounts for the eruption of prominences and coronal mass ejections.

Using high-spatiotemporal-resolution multiwavelength observations from the New Vacuum Solar Telescope and the Solar Dynamics Observatory, we present a detailed analysis of a small-scale chromospheric jet driven by plasmoid-mediated magnetic reconnection. Our results reveal that the entire process is governed by the dynamic evolution of photospheric magnetic footpoints, which proceeds in two distinct stages. An initial separating motion of the footpoints corresponds to a mild reconnection phase, characterized by a short current sheet and the eruption of a cool Hα jet. Subsequently, a converging motion of the footpoints triggers an intense reconnection phase. During this intense stage, the current sheet rapidly elongates, and the resulting decrease in its aspect ratio initiates a tearing-mode instability, forming a plasmoid. The appearance of this plasmoid mediates the onset of fast magnetic reconnection, which produces a hot extreme ultraviolet jet and is concurrent with significant magnetic flux cancellation. We interpret this cancellation as the submergence of newly formed postreconnection loops. Furthermore, we identify a distinct, high-temperature plasma blob in the jet spire, significantly hotter than the surrounding jet plasma. We attribute this feature to a secondary heating process, likely caused by reconnection between the upward-propagating plasmoid and the overlying magnetic cusp structure. These observations provide a comprehensive, observationally driven picture (from the initial photospheric triggers to the multistage plasmoid-mediated reconnection) that forms chromospheric jets, highlighting the critical role of footpoint motions in solar atmospheric dynamics.

We investigate an eruptive M-class flare on 2023 April 21 (SOL2023-04-21T18:12) with observations from the Solar Dynamics Observatory and the Chinese Hα Solar Explorer. We discuss two stages of energy release, the preflare activity and the eruptive flare. The preflare phase features some brightening of the lower atmosphere, the rising motion of filament materials, and a brightening ribbon structure. We suggest that low-altitude magnetic reconnection triggers the eruptive activity. The reconnection between the ambient loops and continuously rising thread-like structures produced the well-formed parallel-ribbon flare. In the main flare phase, the filament experienced a partial eruption with significant plasma motion in the constrained part. We propose a double-decker filament structure based on the multiwavelength observations and analysis of the magnetic field.

Using high spatiotemporal resolution, multi-wavelength observations from the New Vacuum Solar Telescope (NVST) and the Solar Dynamics Observatory (SDO), we present a detailed analysis of a small-scale chromospheric jet driven by plasmoid-mediated magnetic reconnection. Our results reveal that the entire process is governed by the dynamic evolution of photospheric magnetic footpoints, which proceeds in two distinct stages. An initial separating motion of the footpoints corresponds to a mild reconnection phase, characterized by a short current sheet and the eruption of a cool H$α$ jet. Subsequently, a converging motion of the footpoints triggers an intense reconnection phase. During this intense stage, the current sheet rapidly elongates, and the resulting decrease in its aspect ratio initiates a tearing-mode instability, forming a plasmoid. The appearance of this plasmoid mediates the onset of fast magnetic reconnection, which produces a hot EUV jet and is concurrent with significant magnetic flux cancellation. We interpret this cancellation as the submergence of newly formed, post-reconnection loops. Furthermore, we identify a distinct, high-temperature plasma blob in the jet spire, significantly hotter than the surrounding jet plasma. We attribute this feature to a secondary heating process, likely caused by reconnection between the upward-propagating plasmoid and the overlying magnetic cusp structure. These observations provide a comprehensive, observationally driven picture (from the initial photospheric triggers to the multi-stage, plasmoid-mediated reconnection) that forms chromospheric jets, highlighting the critical role of footpoint motions in solar atmospheric dynamics.