David B. Jess

Magnetic oscillations permeating the solar atmosphere can be altered by flares. This could be due to changes in the atmospheric magnetic waveguide, the thermodynamic stratification, or both. To investigate this, we examine oscillations in a magnetic pore crossed in part by the ribbon of a C8.2 flare, using observations from the S unrise Ultraviolet Spectropolarimeter and Imager (SUSI) aboard S unrise iii . We track the core intensities of eight spectral lines between 327–329 nm and show that oscillatory power in the 4.2–7.0 mHz range, measured around 30 minutes after the flare peak, exceeds the preevent value in all eight lines by factors of 1.60–8.71. Conversely, in the 7.0–11.5 mHz band, the postevent intensity power is lower—approximately 0.13–0.41 of the original power in seven of the observed lines. Line-center velocity measurements support the lower-frequency enhancement. This delayed, line-dependent shift toward the lower-frequency band is consistent with flare-induced changes in wave transmission, reflection, or resonant response, although thermodynamic and magnetic effects cannot yet be separated.

One of the first high-cadence chromospheric image sequences recorded with the recently commissioned Daniel K. Inouye Solar Telescope (DKIST) has revealed propagating arc-shaped bright fronts of a few hundred kilometers width. These bright fronts maintain their arc shape over up to one minute, travel with apparent horizontal speeds of ∼8 km s ⁻¹ , and originate from chromospheric bright grains seen at the center of the arc. We identify photospheric G -band bright points underneath the chromospheric bright grains, which are typically the signature of small-scale magnetic flux concentrations. The G -band bright points are found to interact with colocated vortices prior to the appearance of the chromospheric bright fronts. Images synthesized from three-dimensional magnetohydrodynamic simulations show a striking similarity with the discovered phenomenon and reveal that the arc-shaped bright fronts arise from essentially acoustic, weak shock fronts that propagate in the ambient medium, seemingly triggered by the vortex dynamics of the underlying magnetic flux concentration. In this work, we provide the first hints of a hitherto unknown magnetohydrodynamic process by which vortex-driven torsional Alfvén pulses couple to predominantly acoustic waves that steepen into shocks and dissipate their energies. The detected number density and frequency of these events are at least a factor 10 too small to be a major source of solar chromospheric heating but simulations show a seven times higher number density. We therefore expect to discover many more events with tailored narrow band observations.

Context. Three-minute (∼5 mHz) oscillations are a prominent signature of wave propagation in the solar chromosphere, but their measured power can vary substantially between full-disc observations and small, high-resolution fields of view. This variability suggests that the detectability of large-scale chromospheric oscillatory power may depend not only on wave excitation, but also on the magnetic topology through which the waves propagate. Aims. We investigate whether chromospheric magnetic canopy topology, in particular its lateral continuity and areal filling, modulates the field-of-view-averaged three-minute power measured in chromospheric diagnostics. Methods. We analysed high-resolution H α and Ca II 8542 Å spectral imaging from the Swedish 1-m Solar Telescope (SST) and compared canopy-poor quiet-Sun scenes with canopy-dominated active-region environments. These observations were complemented by radiative magnetohydrodynamic (MHD) Bifrost simulations representing canopy-poor and canopy-rich atmospheres. We computed field-of-view-averaged power spectra from pixel-wise fixed-wavelength intensities and bisector-derived line-of-sight velocities in the observations, and from synthetic intensities, vertical velocities, and temperature proxies in the simulations. We also quantified the relation between integrated 3–5 mHz excess power and canopy filling factor in both simulations and observations, using Helioseismic and Magnetic Imager (HMI)-based magnetic-field extrapolations for the latter. Results. In both observations and simulations, canopy-poor scenes show clear enhancements of field-of-view-averaged power in the 3–5 mHz band, whereas canopy-dominated scenes show strongly reduced measured power in the same frequency range. The trend is present in H α and Ca II 8542 Å intensity diagnostics and is supported by complementary velocity and temperature proxies. In both the simulations and SST observations, integrated 3–5 mHz excess power decreases with increasing canopy filling factor. Conclusions. Chromospheric field-of-view-averaged three-minute power is therefore a topology-weighted observable. Dense, laterally continuous magnetic canopies can strongly reduce the measured large-scale three-minute signature without requiring the absence of local wave activity. This effect provides a practical criterion for when chromospheric three-minute power should be recovered in spatially averaged diagnostics and should be considered when interpreting oscillation power as a proxy for atmospheric wave energy in the Sun and, more broadly, in magnetised cool-star atmospheres.

The Ca ii 8542Å line is widely used by modern instruments such as SST/CRISP and DKIST to probe the highly structured and dynamic chromosphere. However, interpreting observations in this line requires a characterisation of the effective height ranges sampled by each spectral tuning, particularly when geometric height is obtained from inversion atmospheres that assume hydrostatic equilibrium. Using high resolution observations of a sunspot, we present a direct comparison between formation-height diagnostics derived from non-LTE radiative-transfer calculations and the geometric heights returned by NICOLE inversions, covering atmospheres corresponding to the umbra, umbral–penumbral boundary, penumbra, and the penumbral–quiet sun boundary. Formation-height probability distributions are computed from Lightweaver contribution functions evaluated in the inversion atmospheres, and convolved with the SST/CRISP transmission profile. We then identify the optical-depth layers whose associated geometric-height distributions from the inversions best match these formation-height probability distributions. We find that the optical-depth range sampled by the line remains broadly stable across the sunspot, whilst the corresponding geometric heights vary systematically in the radial direction. Across the modelled annuli, the selected optical depth intervals remain broadly stable, whilst the corresponding model geometric heights vary with radius. Within the adopted inversion framework, the resulting mapping relates CRISP spectral tunings to optical depth and model geometric height and provides a practical guide for interpreting Ca ii 8542Å observations of chromospheric waves and dynamics, particularly in the era of next-generation facilities such as DKIST.

We present high-resolution multiline spectropolarimetric observations of a quiet-Sun network element obtained with the S unrise iii Chromospheric Infrared SpectroPolarimeter. The observations combine photospheric, upper-photospheric, and chromospheric diagnostics at a spatial resolution and polarimetric sensitivity that allow the transverse magnetic structure of the network boundary to be examined directly. We find that the strongest linear polarization is concentrated in a narrow ridge around the edge of the magnetic element, cospatial with enhanced transverse magnetic field inferred from multiline inversions. The magnetic azimuth exhibits a coherent, predominantly radial organization around a more vertical core, consistent with an expanding magnetic canopy. An azimuth proxy derived directly from the observed Fe i and K i linear polarization reproduces the same large-scale organization, showing that this structure is encoded in the Stokes profiles rather than imposed by the inversion. Response functions and a MURaM-based forward-synthesis test indicate that the Fe i 8468 Å linear polarization is sensitive to magnetic azimuth in the upper photosphere, with the closest proxy agreement occurring near log τ ≈ − 3 . We find no evidence for strong azimuthal shear between the Fe- and K-sensitive diagnostics. At the network boundary, we also identify localized parasitic-polarity patches associated with complex, multilobed Stokes V profiles and one case in which the Stokes V polarity reverses between photospheric Fe i and chromospheric Ca ii lines. These results demonstrate that quiet-Sun network boundaries contain organized upper-photospheric canopy fields together with a small-scale mixed-polarity structure, providing new constraints on the three-dimensional magnetic structure of network elements.

In-game performance monitoring is of growing interest to sports science practitioners. This study presents a proof-of-concept methodology capable of tracking, on average, a 6.4% reduction in ballistic power ( P B ) during competitive matches. The study investigated the linearity of in-situ P F v profiles in 34 sub-elite Gaelic footballers (aged 26.08 ± 6.84 years), compared in-situ to isolated sprint-derived profiles, determined minimum data requirements for producing stable, high-linearity profiles, and explored the utility of in-game monitoring. Linearity was comparable to previous studies, with F v profiles R 2 values of 0.929 ± 0.110 for match data and 0.949 ± 0.105 for training data. Consistent, systematic differences were observed between in-situ and isolated profiles using Cohen’s d . Acceleration ( A 0 ; 1.00 ≤ d ≤ 1.93 ) was significantly higher in-situ, while maximum power ( P max ; − 1.36 ≤ d ≤ − 1.02 ) and the F v offset ( d Fv ; − 1.09 ≤ d ≤ − 0.90 ) were significantly lower, highlighting the two profiles are not interchangeable. Maximum speeds ( S 0 ) exhibited context-dependent variance, being larger in matches than in isolated sprints ( 8.56 ± 0.31 m s ⁻¹ versus 8.33 ± 0.34 m s ⁻¹ ; d = + 0.74 ), but lower in training ( 8.04 ± 0.25 m s ⁻¹ ; d = − 1.29 , p < 0.001 ). Minimum data load was determined via two methods: the time for R 2 to reach 0.9 (12-minutes) and the geometric knee of the R 2 versus data load curve (7-minutes). Using these sliding windows, P B showed average reductions of 4.9% and 6.4%, respectively, across a full game. These findings suggest P F v profiling may offer a practical, scalable method for in-situ performance monitoring in team sports.

Magnetic pores are compact, strongly magnetized waveguides in the lower solar atmosphere and therefore provide favorable conditions for identifying magnetohydrodynamic (MHD) wave modes. Earlier seeing-free observations revealed concurrent sausage, kink, and fluting modes in photospheric pores, but only at a single sampled layer. In this letter, we exploit the dense spectral sampling of the near-ultraviolet 327–329 nm window observed by the S unrise-iii UV Spectropolarimeter and Imager (SUSI) to investigate how pore wave modes behave across multiple photospheric and low-chromospheric heights spanning roughly 500 km. We analyze ∼75 min of a S unrise-iii /SUSI time series containing a small solar pore. From eight selected spectral lines sampling different estimated formation heights, we identify the pore boundary at each line and time step and apply proper orthogonal decomposition (POD) to the boundary oscillations. In all eight lines, the first POD mode is consistently identified as an axisymmetric sausage mode, with dominant power at ∼1–2 mHz, and carries the dominant normalised eigenvalue fraction, typically about 66%–86%, while the second mode is a fluting mode with azimuthal wave number m = 2, dominant at ∼2–3.5 mHz, and contributes about 4%–10%. Cross-line wavelet phase analysis of the temporal coefficients shows that the sausage mode remains close to zero phase difference across the sampled heights, consistent with standing or near-standing behaviour, whereas the fluting mode displays a modest but systematic increase in phase with height, reaching about 50°, indicative of an upward-propagating component. These observations provide the first multiheight identification and phase characterisation of sausage and fluting modes inferred from pore-boundary oscillations.

Magnetohydrodynamic waves redistribute energy in magnetic structures of the lower solar atmosphere, yet constraints on how wave power and dominant frequencies are organized above sunspots remain limited, because most studies use only a few well-separated diagnostics. Here, we present multiline wave signatures in a sunspot from near-ultraviolet (near-UV) spectroscopy with the S unrise-iii UV Spectropolarimeter and Imager (SUSI). We analyse a 2 hr time series of repeated raster scans of a sunspot near disc center in the 327–329 nm spectral window (>100 lines). From these, we select 44 lines that radiative-transfer calculations suggest sample effective formation heights within the umbral core, from the deep photosphere toward the low chromosphere. For each line, we extract line-core intensity and line-of-sight velocity time series using a dedicated multiline fitting routine and compute Morlet wavelet power spectra. The refined global wavelet spectra show that most lines (in both intensity and velocity) are genuinely multifrequency, with a dominant peak and substantial statistically significant power up to 12 mHz. Unsupervised clustering of the normalized spectra groups lines into families with similar spectral shapes and reveals a progression of dominant frequencies from ∼2 to ∼10 mHz across the ensemble, for both intensity and velocity (not necessarily in the same lines). This behavior is not reproduced by a simple formation-height ranking, suggesting that uncertainties in the formation-height estimates and line-dependent diagnostic response together shape the ordering. These S unrise-iii /SUSI observations open a new regime for near-UV multiline wave studies and provide the first systematic characterization of frequency-structured sunspot wave behaviour in this spectral region.

We present a multiline characterization of how oscillatory power is organized across distinct magnetic environments in an active region using seeing-free, stratospheric near-ultraviolet (near-UV) spectroscopy from the S unrise iii UV Spectropolarimeter and Imager (SUSI). A 2 hr time series of short raster scans in the line-rich 327–329 nm window samples along a single transect that contains the following regions: weak magnetic field surroundings, a plage, a sunspot, and a pore. From a set of 30 selected, relatively unblended absorption lines, we extract line-core Doppler velocity time series and compute Morlet-wavelet refined global spectra from which we form band-integrated power maps for three frequency bands (2–4, 4–6, and 6–12 mHz). The stacked, line-resolved maps reveal a clear environment-dependent redistribution of power: 2–4 mHz power is strongest in the weak-field/plage segments but is commonly suppressed in the umbra and pore cores, while 4–6 mHz and 6–12 mHz power becomes relatively enhanced in the strongest-field regions, with line-dependent behavior in the penumbra and plage. Across the line ensemble, this broad frequency structuring is coherent, but the detailed spatial distribution and relative band ranking are not identical from line to line—even among spectral lines with comparable effective formation depths—demonstrating clear line dependence. This novel result implies that single-line measurements may miss secondary components of the local wave spectrum because different lines weight coexisting perturbations and modes differently; therefore, the SUSI near-UV window provides a uniquely diagnostic-rich mapping of oscillations, offering leverage that is difficult to obtain with traditional one- or two-line approaches.

Bright points (BPs) are small-scale, dynamic features that are ubiquitous across the solar disc and are often associated with the underlying magnetic field. Using broadband photospheric images obtained with the Visible Broadband Imager at the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), the properties of BPs have been analyzed with DKIST for the first time at the highest spatial resolutions achievable. BPs were observed to have an average lifetime of 95 ± 29 s and a mean transverse velocity of 1.60 ± 0.41 km s ⁻¹ . The BPs had a log-normal area distribution with a peak at 2300 km ² . Transverse velocities and lifetimes across the DKIST images were comparable and consistent with previous studies. The area distribution of the DKIST data peaked in areas significantly lower than those from the literature. This was explored further and was observed to be due to an overestimation of BP areas due to the merging of close features when the spatial resolution is reduced, in tandem with possible oversplitting of features in the DKIST images. Furthermore, the effect of variable seeing in the data was determined. This showed that the average spatial resolution of the data was around 0 . ″ 034 ± 0 . ″ 007 , in comparison to the theoretical diffraction limit of 0 . ″ 022 . Accounting for the influence of seeing, the peak of the area distribution of BPs in the DKIST data was estimated as 4800 km ² , which is still significantly lower than previously observed.