Solar Telescope Research Articles

Formation and Eruption of a Hot Channel Magnetic Flux Rope in a Nested Double Null Magnetic System

The coronal magnetic topology significantly affects the outcome of magnetic flux rope (MFR) eruptions. The recently reported nested double null magnetic system remains unclear as to how it affects MFR eruptions. Using observations from the New Vacuum Solar Telescope and the Solar Dynamics Observatory, we studied the formation and successful eruption of a hot channel MFR from NOAA active region AR 12173 on 2014 September 28. We observed that a hot channel MFR formed and erupted as a coronal mass ejection (CME), and the magnetic field of the source region was a nested double null magnetic system in which an inner magnetic null point system was nested by an outer fan–spine magnetic system. Observational analysis suggests that the origin of the MFR was due to magnetic reconnection at the inner null point, which was triggered by the photospheric swirling motions. The long-term shearing motion in the source region throughout around 26 hr might accumulate enough energy to power the eruption. Since previous studies showed that MFR eruptions from nested double null magnetic systems often result in weak jets and stalled or failed eruptions, it is hard to understand the generation of the large-scale CME in our case. A detailed comparison with previous studies reveals that the birth location of the MFR relative to the inner null point might be the critical physical factor for determining whether an MFR can erupt successfully or not in such a particular nested double null magnetic system.

Magnetic diffusion in solar atmosphere produces measurable electric fields

The efficient release of magnetic energy in astrophysical plasmas, such as during solar flares, can in principle be achieved through magnetic diffusion, at a rate determined by the associated electric field. However, attempts at measuring electric fields in the solar atmosphere are scarce, and none exist for sites where the magnetic energy is presumably released. Here, we present observations of an energetic event using the National Science Foundation’s Daniel K. Inouye Solar Telescope, where we detect the polarization signature of electric fields associated with magnetic diffusion. We measure the linear and circular polarization across the hydrogen Hε Balmer line at 397 nm at the site of a brightening event in the solar chromosphere. Our spectro-polarimetric modeling demonstrates that the observed polarization signals can only be explained by the presence of electric fields, providing conclusive evidence of magnetic diffusion, and opening a new window for the quantitative study of this mechanism in space plasmas.

The Observational and Numerical Analysis of the Rayleigh–Taylor Instability beneath a Hedgerow Prominence

Using Swedish 1 m Solar Telescope Crisp Imaging Spectro-Polarimeter 6563 Å (Hα) observations and Mancha3D simulations, we analyze the formation and evolution of falling knots beneath a hedgerow prominence. By comparing the observed knot widths and kinematics to those of a parametric survey of simulations, we estimate the range of magnetic field values and characteristic wavelengths to test if the magnetic Rayleigh–Taylor instability (MRTI) can provide a physically meaningful explanation. We recover observational parameters using a novel semiautomated method and find knot velocities with a mean of −9.68 km s−1 and a mean width of 614 km. Our simulations survey a range of critical wavelengths, λ c , of 100 to 500 km, and magnetic field strengths, B 0, of 1 to 20 G, finding the closest match to observations around λ c = 300 km, and B 0 = 2 to 6 G. As both the observational and simulated values match expected values, we conclude that the MRTI can provide a physically meaningful explanation of this observation. Additionally, we also predict that the Daniel K. Inouye Solar Telescope will be able to observationally recover secondary instabilities on the leading edge of the falling mass through applying a point-spread function to an example from the simulated results.

Sun-as-a-star Analysis of the X1.6 Flare on 2023 August 5: Dynamics of Postflare Loops in Spatially Integrated Observational Data

Postflare loops are loop-like plasmas observed during the decay phase of solar flares, and they are expected to exist for stellar flares. However, it is unclear how postflare loops are observed in stellar flares’ cases. To clarify behaviors of postflare loops in spatially integrated data, we performed the Sun-as-a-star analysis of the X1.6 flare that occurred on 2023 August 5, using GOES X-ray flux (∼107 K), extreme ultraviolet (EUV) images taken by Atmospheric Imaging Assembly on board the Solar Dynamic Observatory (≥104.9 K), and Hα data taken by Solar Dynamics Doppler Imager on board the Solar Magnetic Activity Research Telescope at Hida Observatory, Kyoto University (∼104 K). As a result, we found that this flare showed signatures corresponding to the important dynamics of the postflare loops even in the spatially integrated data: (1) The Hα light curve showed two distinct peaks corresponding to the flare ribbons and the postflare loops. The plasma cooling in the postflare loops generated different peak times in soft X-rays, EUV, and Hα light curves. (2) Downflows were confirmed as simultaneous redshifted/blueshifted absorptions in the Hα spectra. (3) The apparent rise of postflare loops was recognized as a slowing of the decay for the Hα light curve. These results are the key to investigating stellar postflare loops with spatially integrated data. We also discuss the dependence of our results on flare locations and their possible applications to stellar observations.

Using the Cartwheel CME to Predict Off-limb Observations of CMEs for New and Upcoming UV and EUV Spectrometers

Coronal mass ejections (CMEs) expel multithermal, magnetized plasma from the Sun, and when directed toward Earth, can cause extensive damage to space and ground-based electronics. To better understand the triggering, acceleration, and evolution of CMEs, it is critical to study CME plasma properties close to the Sun. High-resolution ultraviolet and extreme ultraviolet (UV-EUV) spectroscopy can give the most detailed plasma diagnostics of CMEs in the low solar corona. Unfortunately, very few spectrally resolved observations of CMEs in the low solar corona exist. However, with the recent launch of the Spectral Imaging of the Coronal Environment on board Solar Orbiter and the upcoming missions, including the EUV High-Throughput Solar Telescope (EUVST) on Solar-C and the Multi-slit Solar Explorer (MUSE), we will have the opportunity to obtain unprecedented, spectrally resolved CME observations. Using the only full EUV spectral observation of a CME by the Hinode/EUV Imaging Spectrometer, we predict the spectra that SPICE, EUVST, and MUSE are expected to observe during an off-limb CME eruption to investigate the diagnostic capabilities of each instrument. Finally, we provide a list of density-sensitive and temperature-sensitive ratios for CME plasma diagnostics along with the expected spectral atlas for each instrument to facilitate observing sequence planning.

High-resolution Imaging Spectroscopy of a Tiny Sigmoidal Minifilament Eruption

Minifilament eruptions producing small jets and microflares have mostly been studied based on coronal observations at extreme-ultraviolet and X-ray wavelengths. This study presents chromospheric plasma diagnostics of a quiet-Sun minifilament of size ∼ 2″ × 5″ with a sigmoidal shape and an associated microflare observed on 2021 August 7 17:00 UT using high temporal and spatial resolution spectroscopy from the Fast Imaging Solar Spectrograph (FISS) and high-resolution magnetograms from the Near InfraRed Imaging Spectropolarimeter (NIRIS) installed on the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory. Using FISS Hα and Ca ii 8542 Å line spectra at the time of the minifilament activation we determined a temperature of 8600 K and a nonthermal speed of 7.9 km s−1. During the eruption, the minifilament was no longer visible in the Ca ii 8542 Å line, and only the Hα line spectra were used to find the temperature of the minifilament, which reached 1.2 × 104 K and decreased afterward. We estimated thermal energy of 3.6 × 1024 erg from the maximum temperature and kinetic energy of 2.6 × 1024 erg from the rising speed (18 km s−1) of the minifilament. From the NIRIS magnetograms we found small-scale flux emergence and cancellation coincident with the minifilament eruption, and the magnetic energy change across the conjugate footpoints reaches 7.2 × 1025 erg. Such spectroscopic diagnostics of the chromospheric minifilament complement earlier studies of minifilament eruptions made using coronal images.

Direct Imaging of a Prolonged Plasma/Current Sheet and Quasiperiodic Magnetic Reconnection on the Sun

Magnetic reconnection is widely believed to be the fundamental process in the solar atmosphere that underlies magnetic energy release and particle acceleration. This process is responsible for the onset of solar flares, coronal mass ejections, and other explosive events (e.g., jets). Here, we report direct imaging of a prolonged plasma/current sheet along with quasiperiodic magnetic reconnection in the solar corona using ultra-high-resolution observations from the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory and the Solar Dynamics Observatory/Atmospheric Imaging Assembly. The current sheet appeared near a null point in the fan–spine topology and persisted over an extended period (≈20 hr). The length and apparent width of the current sheet were about 6″ and 2″, respectively, and the plasma temperature was ≈10–20 MK. We observed quasiperiodic plasma inflows and outflows (bidirectional jets with plasmoids) at the reconnection site/current sheet. Furthermore, quasiperiodic reconnection at the long-lasting current sheet produced recurrent eruptions (small flares and jets) and contributed significantly to the recurrent impulsive heating of the active region. Direct imaging of a plasma/current sheet and recurrent null-point reconnection for such an extended period has not been reported previously. These unprecedented observations provide compelling evidence that supports the universal model for solar eruptions (i.e., the breakout model) and have implications for impulsive heating of active regions by recurrent reconnection near null points. The prolonged and sustained reconnection for about 20 hr at the breakout current sheet provides new insights into the dynamics and energy release processes in the solar corona.

High-resolution observations of recurrent jets from an arch filament system

Solar jets are collimated plasma ejections along magnetic field lines observed in hot (extreme-ultraviolet (EUV) jets) and cool (chromospheric surges) temperature diagnostics. Their trigger mechanisms and the relationship between hot and cool jets are still not completely understood. We aim to investigate the generation of a sequence of active-region solar jets and their evolution from the photospheric to the coronal heights using multithermal observations from ground-based and space-borne instruments. Using the synergy of high-spatial-resolution and high-temporal-resolution observations by the Swedish 1-m Solar Telescope (SST), along with the Solar Dynamics Observatory (SDO), we analyzed a sequence of solar jets originating in a mixed-polarity region between the leading and following sunspots of an active region. We investigated the kinematics of these jets using the spectra from the SST observations. We used a non-force-free field (NFFF) extrapolation technique to derive the magnetic field topology of the active region. A mixed-polarity region is formed over a long period (24 hours) with persistent magnetic flux emergence. This region has been observed as an arch filament system (AFS) in chromospheric SST observations. In this region, negative polarities surrounded by positive polarities create a fan surface with a null point at a height of 6 Mm detected in the NFFF extrapolation. SST observations in the Hbeta spectral line reveal a large flux rope over the AFS moving from north to south, causing successive EUV and cool jets to move in the east--west direction and later towards the south along the long open loops. The high-resolution SST observations (0 per pixel) resolve the dark area observed at the jet base and reveal the existence of an AFS with an extended cool jet, which may be the result of a peeling-like mechanism of the AFS. Based on the combined analysis of SST and AIA observations along with extrapolated magnetic topology, it is suggested that the magnetic reconnection site may move southward by approximately 20 Mm until it reaches a region where the open magnetic field lines are oriented north--south.

A search for mode coupling in magnetic bright points

Magnetic bright points (MBPs) are one of the smallest manifestations of the magnetic field in the solar atmosphere and are observed to extend from the photosphere up to the chromosphere. As such, they represent an excellent feature to use in searches for types of magnetohydrodynamic (MHD) waves and mode coupling in the solar atmosphere. In this work, we aim to study wave propagation in the lower solar atmosphere by comparing intensity oscillations in the photosphere with the chromosphere via a search for possible mode coupling, in order to establish the importance of these types of waves in the solar atmosphere, and their contribution to heating the chromosphere. These observations were conducted in July 2011 with the Rapid Oscillations of the Solar Atmosphere (ROSA) and the Hydrogen-Alpha Rapid Dynamics Camera (HARDCam) instruments at the Dunn Solar Telescope. Observations with good seeing were made in the G-band and Halpha wave bands. Speckle reconstruction and several post facto techniques were applied to return science-ready images. The spatial sampling of the images was 0.069arcsec /pixel (50 km/pixel). We used wavelet analysis to identify traveling MHD waves and derive frequencies in the different bandpasses. We isolated a large sample of MBPs using an automated tracking algorithm throughout our observations. Two dozen of the brightest MBPs were selected from the sample for further study. We find oscillations in the G-band MBPs, with frequencies between 1.5 and 3.6 mHz. Corresponding MBPs in the lower solar chromosphere observed in Halpha show a frequency range of 1.4 to 4.3 mHz. In about 38<!PCT!> of the MBPs, the ratio of Halpha to G-band frequencies was near two. Thus, these oscillations show a form of mode coupling where the transverse waves in the photosphere are converted into longitudinal waves in the chromosphere. The phases of the Halpha and G-band light curves show strong positive and negative correlations only 21<!PCT!> and 12<!PCT!> of the time, respectively. From simple estimates we find an energy flux of approx 45 $ $ W m$^ $ and show that the energy flowing through MBPs is enough to heat the chromosphere, although higher-resolution data are needed to explore this contribution further. Regardless, mode coupling is important in helping us understand the types of MHD waves in the lower solar atmosphere and the overall energy budget.

Transition region response to quiet-Sun Ellerman bombs

Context. Quiet-Sun Ellerman bombs (QSEBs) are key indicators of small-scale photospheric magnetic reconnection events. Recent high-resolution observations have shown that they are ubiquitous and that large numbers of QSEBs can be found in the quiet Sun. Aims. We aim to understand the impact of QSEBs on the upper solar atmosphere by analyzing their spatial and temporal relationship with the UV brightenings observed in transition region diagnostics. Methods. We analyzed high-resolution Hβ observations from the Swedish 1-m Solar Telescope and utilized k-means clustering to detect 1423 QSEBs in a 51 min time series. We used coordinated and co-aligned observations from the Interface Region Imaging Spectrograph (IRIS) to search for corresponding signatures in the 1400 Å slit-jaw image (SJI) channel and in the Si IV 1394 Å and Mg II 2798.8 Å triplet spectral lines. We identified UV brightenings from SJI 1400 using a threshold of 5σ above the median background. Results. We focused on 453 long-lived QSEBs (> 1 min) and found 67 cases of UV brightenings from SJI 1400 occurring near the QSEBs, both temporally and spatially. Temporal analysis of these events indicates that QSEBs start before UV brightenings in 57% of cases, while UV brightenings lead in 36% of instances. The majority of the UV brightenings occur within 1000 km of the QSEBs in the direction of the solar limb. We also identify 21 QSEBs covered by the IRIS slit, four of which show emissions in the Si IV 1394 Å and/or Mg II 2798.8 Å triplet lines, at distances within 500 km of the QSEBs in the limb direction. Conclusions. We conclude that a small fraction (15%) of the long-lived QSEBs contribute to the localized heating observable in transition region diagnostics, indicating they play a minimal role in the global heating of the upper solar atmosphere.

Parallel Analogy Method for Measuring FRD of the FASOT-IFU

A fiber integral field unit (IFU) was chosen for the Fiber Array Solar Optical Telescope (FASOT) to obtain high-spectral-resolution polarization solar spectral images. This IFU features a dual-array-end design, complemented by a dozen slit ends. Each consists of 2 sub-slits corresponding to the dual array ends. In order to accurately and quickly measure the focal ratio degradation of 8064 fibers in FASOT-IFU, a parallel analogy method (PAM) for FASOT-IFU was proposed. This method primarily relies on characterizing the focal ratio based on the full-width at half-maximum (FWHM) of the fiber’s output spot, and the linear relationship between the output focal ratio of the spot and the FWHM. By precisely calculating the focal ratio of the positioning fiber in the FASOT-IFU and treating it as a reference, the output focal ratio of the working fiber can be obtained by comparing the FWHM of the working fiber spot and the positioning fiber spot at the same emission distance. The average value of the output focal ratio by PAM corresponding to the 4032 fibers from Array A of the IFU is 6.0 and the standard deviation is 0.6. The values corresponding to the Array B are 6.2 and 0.40, respectively. The mean value exceeds the contractually specified F/5.5, and the proportion of optical fibers with a focal ratio greater than 5.5 accounts for 88% of the total number of optical fibers, meeting the design requirements of the FASOT system.

A Data-constrained Analysis for Joule Heating as a Solar Active Region Atmosphere Heating Mechanism. I. Sunspot Umbral Light Bridge

Understanding the mechanisms underlying the heating of the solar atmosphere is a fundamental problem in solar physics. The lower atmosphere of the Sun (i.e., photosphere and chromosphere) is composed of weakly ionized plasma. This results in anisotropic dissipation of electric currents by Coulomb and Cowling resistivities. Joule heating due to dissipation of currents perpendicular to the magnetic field by Cowling resistivity has been demonstrated to be the main mechanism for the heating of a sunspot umbral light bridge located in NOAA AR 12002 on 2014 March 13. Here, we focus on the same target region and demonstrate the importance of further constraining our Joule heating model using observational data in addition to magnetic field, namely plasma temperature calculated from the inversion of spectroscopic data obtained from the Interferometric BI-dimensional Spectrometer instrument of the ground-based Dunn Solar Telescope. As a parameter in our analysis, temperature is demonstrated to have the highest sensitivity after magnetic field. We show that the heating of the light bridge is a highly dynamic event that necessitates utilization of 3D spatially resolved observational data for temperature rather than a 1D temperature stratification based on theoretical/semiempirical solar atmosphere models. Our improved data-constrained analysis using spatially resolved temperatures shows that the entire light bridge is heated by the proposed mechanism, and yields heating rate values that are consistent with our previous study.

Filamentary Structures Formation around a Magnetic Pore Using High-resolution Observations of the Goode Solar Telescope

With the aid of high-resolution spatial and temporal observations from the Goode Solar Telescope, we present an investigation of the emergence, coalescence, and submergence of a moving magnetic feature (MMF) in the region surrounding a magnetic pore located at the periphery of a large sunspot. The results show that the MMF has a magnetic field strength greater than 500 G and is dominated by the horizontal magnetic component. We observe upflow at the inner part and downflow at the outer part, indicating a pattern of Evershed flow. The MMF emergence is accompanied by the expansion of a granule, which has several striations inside just like the twisted features found in the penumbra filament. Our analysis shows that although these striations have different properties of magnetic field and kinematics during the expansion of the granule, the overall magnetic and dynamic properties of the MMF remain stable. We find that the region where the MMF emerges and submerges becomes more penumbra-like, i.e., adjacent positive and negative values of elongated magnetic features that are parallel to each other, while the optical penumbra-like features are not apparent at the same time. Our work indicates that the dynamics of the MMF near the magnetic pore is important for the development of filamentary structure. The magnetic configuration produced by an MMF together with the elongation of a granule could thus be key to understand the formation of penumbra filaments.

Investigation of Phase Shift and Travel Time of Acoustic Waves in the Lower Solar Atmosphere Using Multiheight Velocities

We report and discuss the phase shift and phase travel time of low-frequency (ν < 5.0 mHz) acoustic waves estimated within the photosphere and photosphere–chromosphere interface regions, utilizing multiheight velocities in the quiet Sun. The bisector method has been employed to estimate seven height velocities in the photosphere within the Fe i 6173 Å line scan, while nine height velocities are estimated from the chromospheric Ca ii 8542 Å line scan observations obtained from the narrowband imager instrument installed on the Multi-Application Solar Telescope operational at the Udaipur Solar Observatory, India. Utilizing a fast Fourier transform at each pixel over the full field of view, phase shift and coherence have been estimated. The frequency and height-dependent phase shift integrated over the regions having an absolute line-of-sight magnetic field of less than 10 G indicates the nonevanescent nature of low-frequency acoustic waves within the photosphere and photosphere–chromosphere interface regions. Phase travel time estimated within the photosphere shows nonzero values, aligning with previous simulations and observations. Further, we report that the nonevanescent nature persists beyond the photosphere, encompassing the photospheric–chromospheric height range. We discuss possible factors contributing to the nonevanescent nature of low-frequency acoustic waves. Additionally, our observations reveal a downward propagation of high-frequency acoustic waves indicating refraction from higher layers in the solar atmosphere. This study contributes valuable insights into the understanding of the complex dynamics of acoustic waves within different lower solar atmospheric layers, shedding light on the nonevanescent nature and downward propagation of the acoustic waves.

Various Features of the X-class White-light Flares in Super Active Region NOAA 13664

Super active region NOAA 13664 produced 12 X-class flares (including the largest one so far, an occulted X8.7 flare, in solar cycle 25) during 2024 May 8–15, and 11 of them are identified as white-light flares. Here we present various features of these X-class white-light flares observed by the White-light Solar Telescope (WST) on board the Advanced Space-based Solar Observatory and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. It is found that both the white-light emissions at WST 3600 Å (Balmer continuum) and HMI 6173 Å (Paschen continuum) show up in different regions of the sunspot group in these flares, including outside the sunspots and within the penumbra and umbra of the sunspots. They exhibit a point-, ribbon-, loop-, or ejecta-like shape, which can come from flare ribbons (or footpoints), flare loops, and plasma ejecta depending on the perspective view. The white-light duration and relative enhancement are measured and both parameters for 3600 Å emission have greater values than those for 6173 Å emission. It is also found that these white-light emissions are cospatial well with the hard X-ray (HXR) sources in the on-disk flares but have some offsets with the HXR emissions in the off-limb flares. In addition, it is interesting that the 3600 and 6173 Å emissions show different correlations with the peak HXR fluxes, with the former one more sensitive to the HXR emission. All these greatly help us understand the white-light flares of a large magnitude from a super active region on the Sun and also provide important insights into superflares on Sun-like stars.

Very Long-periodic Pulsations Detected Simultaneously in a White-light Flare and Sunspot Penumbra

We investigate the origin of very long-periodic pulsations in the white-light emission of an X6.4 flare on 2024 February 22 (SOL2024-02-22T22:08), which occurred at the edge of a sunspot group. The flare white-light fluxes reveal four successive and repetitive pulsations, which are simultaneously measured by the Helioseismic and Magnetic Imager and the White-light Solar Telescope. A quasi-period of 8.6−1.9+1.5 minutes, determined by the Morlet wavelet transform, is detected in the visible continuum channel. The modulation depth, which is defined as the ratio between the oscillatory amplitude and its long-term trend, is smaller than 0.1%, implying that the quasi-periodic pulsation (QPP) feature is a weak wave process. Imaging observations show that the X6.4 flare occurs near a sunspot group. Moreover, the white-light brightening is located in sunspot penumbra, and a similar quasi-period of about 8.5 −1.8+1.6 minutes is identified in one penumbral location of the nearest sunspot. The map of Fourier power distribution suggests that a similar periodicity is universally existing in most parts of the penumbra that is close to the penumbral–photospheric boundary. Our observations support the scenario that the white-light QPP is probably modulated by the slow-mode magnetoacoustic gravity wave leaking from the sunspot penumbra.

Cooling air flow field in the primary mirror temperature control system of a solar telescope

The temperature distribution and the difference with the ambient temperature of the primary mirror are crucial factors affecting the observational quality of the solar telescope. We designed a flow field structure of the primary mirror temperature control system based on the 2.5-meter Wide-field and High-resolution Solar Telescope(WeHoT), analyzed the flow conditions and heat transfer capacity of the overall flow field, and then carried out five stages of optimization iteration and simulation guided by the analysis results. A flow field structure for the primary mirror temperature control system with high efficiency and high uniformity is summarized. The simulation results for the final solution indicate an average surface temperature of the primary mirror at 20.064°C, with a maximum temperature difference within the reflective surface of 0.809°C, and a reduced difference with the ambient temperature of 0.411°C. Surface thermal deformation is less than 0.2 μm, with an RMS value of 18.05 nm, achieving the ideal state. This work can provide a theoretical foundation and valuable insights for future research on the temperature control system of the primary mirror in large-aperture solar telescopes.

Inflight Performance and Calibrations of the Lyman-Alpha Solar Telescope on Board the Advanced Space-Based Solar Observatory

Inflight Performance and Calibrations of the Lyman-Alpha Solar Telescope on Board the Advanced Space-Based Solar Observatory

Observations of Locally Excited Waves in the Low Solar Atmosphere Using the Daniel K. Inouye Solar Telescope

We present an interpretation of the recent Daniel K. Inouye Solar Telescope (DKIST) observations of propagating wave fronts in the lower solar atmosphere. Using MPS/University of Chicago MHD radiative magnetohydrodynamic simulations spanning the solar photosphere, the overshoot region, and the lower chromosphere, we identify three acoustic-wave source mechanisms, each occur at a different atmospheric height. We synthesize the DKIST Visible Broadband Imager G-band, blue-continuum, and Ca ii K signatures of these waves at high spatial and temporal resolution, and conclude that the wave fronts observed by DKIST likely originate from acoustic sources at the top of the solar photosphere overshoot region and in the chromosphere proper. The overall importance of these local sources to the atmospheric energy and momentum budget of the solar atmosphere is unknown, but one of the excitation mechanisms identified (upward propagating shock interaction with down-welling chromospheric plasma resulting in acoustic radiation) may be an important shock dissipation mechanism. Additionally, the observed wave fronts may prove useful for ultralocal helioseismological inversions and promise to play an important diagnostic role at multiple atmospheric heights.

Unraveling the untwisting process and upward mass transfer of a twisted prominence driven by vortex motion

Solar filaments or prominences are common features in the Sun's atmosphere that contain cool chromospheric material suspended within the hot corona. However, the intricate topology of these structures and the mechanisms driving their instability and upward material transfer are not well understood. Investigating these issues is essential for gaining insight into the fundamental laws that govern solar activity. This study is to analyze a specific twisted prominence observed on February 10, 2021, and to explore its dynamics, including stability, motion, and material transfer. The study also aims to propose a mechanism, based on the K\'arm\'an Vortex Street instability, to explain the destabilization of the prominence. The study utilizes high-resolution H$_ alpha $ observations from the 1-m New Vacuum Solar Telescope and space-borne observations from the Solar Dynamics Observatory. These observations capture the characteristics and behavior of the twisted prominence. We analyzed the data to investigate the equilibrium state, subsequent destabilization, vortex motion, oscillations, resonations, untwisting, and upward mass loading of the prominence. We also detected and measured the speeds of outflows surrounding the prominence. The study reveals that the observed twisted prominence exhibited a stretched and twisted structure at its apex, distinguishing it from familiar cloudy prominences. Following a period of more than 30 hours in equilibrium, the prominence underwent destabilization, leading to a series of dynamic phenomena, such as vortex motion, oscillations, resonations, untwisting, and the upward transfer of mass. Consequently, material from the top of the prominence was carried upward and deposited into the overlying magnetic arcades. Noteworthy, outflows surrounding the prominence were characterized by speeds exceeding 40 km s$^ Based on these findings, we propose, for the first time, a mechanism rooted in the K\'arm\'an Vortex Street instability to explain the destabilization of the prominence. The estimated typical Strouhal Number of 0.23pm 0.06, which is related to vortex shedding, falls within the expected range for the K\'arm\'an Vortex Street effect, as predicted by simulations. These discoveries provide new insights into the dynamics and fundamental topology of solar prominences and reveal a previously unknown mechanism for mass loading into the upper atmosphere.