Abstract S unrise iii is a stratospheric balloon-borne solar observatory with a 1 m diameter telescope and three postfocus instruments, along with an image stabilisation system, all within a protective gondola. It samples the lower solar atmosphere, from the solar surface to the middle chromosphere, at a resolution approaching 50 km on the Sun. S unrise iii flew successfully for 6.5 days suspended from a zero-pressure stratospheric balloon from northern Sweden to northwestern Canada in 2024 July, gathering around 200 TB of data. The present issue of the Astrophysical Journal Letters focuses on the first scientific results from the data collected during that flight. This Letter introduces this Focus Issue, providing a very brief overview of the capabilities of the instrumentation, the flight, and of the gathered data. Challenges for the measurements, data reduction, and interpretation are also briefly touched upon. The Letter ends with an overview of the first set of science results obtained from these data, as presented in the current Focus Issue.

The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) instrument on board the balloon-borne S unrise iii observatory provided new high-resolution observations of the solar chromosphere in the Ca ii λ 854.2 nm line. The Stokes V signal in magnetic network regions was found to show fine-structured details, which suggests the magnetic field above the network elements does not simply expand as a unipolar feature but displays opposite-polarity intrusions (OPIs). These features appear as elongated structures in Stokes V observations. In this work, we demonstrate that such features appear ubiquitously in a numerical simulation of the solar chromosphere. We use a simulation that is computed with the recently developed chromospheric extension of MURaM (MURaM-ChE) and resembles an enhanced network region. We find that OPIs appear ubiquitously in the vertical component of the magnetic field at around 1 Mm above the surface and are visible in the synthetic Stokes V signal of the Ca ii λ 854.2 nm line. The structures have lengths of ≈2–7 Mm and widths of approximately 1 Mm. The magnetic field configurations associated with the OPI features appear to belong to twisted flux ropes and are visible for most of the time in the presented 21 minutes time series. Our results show that the magnetic structure of the chromosphere is more complex than previously thought, with even seemingly simple flux tubes showing embedded twisted fields pointing in the opposite direction. This may help in explaining new high-resolution observations from the S unrise iii mission.

This paper describes the wave-front correction and image stabilisation system (CWS) developed for the Sunrise III balloon-borne telescope, and provides information about its performance as measured during the integration into the telescope and during the 2024 science flight. The fast image stabilisation is done by a correlation tracker (CT) and a fast tip-tilt mirror, low order aberrations such as defocus and coma are measured by a six-element Shack-Hartmann wavefront sensor (WFS) and corrected by an active telescope secondary mirror for automated focus and manual coma correction. The CWS is specified to deliver a stabilised image with a precision of 0.005 arcsec (rms). The autofocus adjustment is specified to maintain a focus stability of 0.01 waves in the focal plane of the CWS.

Using high-resolution observations from the TuMag instrument aboard the Sunrise iii solar observatory balloon mission, we investigate solar vortices in the lower atmosphere. First, we identify vortices by extracting coherent dynamical patterns from intensity data using morphological analysis combined with spectral proper orthogonal decomposition applied to Mg I time series that probe the photosphere and lower chromosphere. We found that ∼8.5 × 10 ^4 vortices may be present on the Sun at any given time, with an average lifetime of $\tau \approx 27\,\mathrm{minutes}$ . To investigate vortex-mediated cross-layer coupling, we apply Granger causality (GC), which tests whether past fluctuations in one atmospheric layer carry statistically significant predictive power for future fluctuations in another, serving as a statistical proxy for directed dynamical coupling potentially associated with energy and momentum transfer. A pixel-to-pixel GC analysis reveals enhanced and spatially organized lower-atmospheric coupling within vortices, with statistically dominant photosphere-to-chromosphere influence in some locations and the reverse in others. This locally enhanced bidirectional spatial pattern of influence presents morphology consistent with the vortex-driven vertical Poynting flux distribution predicted by numerical simulations, suggesting that the coupling inferred from GC traces dynamical interactions associated with vortex-driven energy transport across atmospheric layers. On average, the directional asymmetry favors photosphere-to-chromosphere predictive coupling. Within vortex regions, past photospheric fluctuations provide ≈53% stronger predictive power for future chromospheric fluctuations than in nonvortex regions over a lag of 4.5 minutes. These results provide the first observational evidence of enhanced information transfer between atmospheric layers associated with solar vortices.

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.

The relative prevalence of horizontal and vertical magnetic fields in the quiet-Sun internetwork remains debated, owing to the weak linear polarisation signals that make the inferred magnetic inclination distributions sensitive to observational quality and inversion methodology. We investigate the magnetic topology of the quiet-Sun internetwork in Sunrise iii observations by independently applying transformer-based and traditional inversion techniques to the same spectropolarimetric dataset. We analyse observations obtained with the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP). Transformer-based inversions (SINN), trained exclusively on synthetic Stokes profiles generated from a large radiative magnetohydrodynamic simulation, are compared with independent inversions performed using the DeSIRe code. Both inversion methods recover a quiet-Sun magnetic topology in which internetwork fields are strongly dominated by the horizontal component, whereas network fields exhibit a substantially more balanced topology. At =-1.2, the median horizontal and unsigned line-of-sight field components in the internetwork are 64 and 7G with DeSIRe, and 71 and 8G with SINN, respectively, corresponding to a horizontal-to-line-of-sight ratio of approximately nine for both methods. The agreement between the two fundamentally different inversion methodologies indicates that the quiet-Sun internetwork is characterised by a substantially stronger horizontal than vertical magnetic field component. These results demonstrate that transformer-based inversions can be successfully transferred from synthetic training data to real spectropolarimetric observations, while providing inference orders of magnitude faster than traditional inversion techniques.

Ellerman bombs (EBs) are widely recognized as photospheric and chromospheric signatures of magnetic reconnection. However, the 3D magnetic topology has remained elusive due to the lack of seamless height coverage in observations. Here, we present initial results from the S unrise iii /Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) observations of an emerging flux region. Exploiting the seeing-free, high-spatial-resolution observations provided by the 1 m balloon-borne telescope, SCIP achieved seamless multiline spectropolarimetry from the photosphere to the lower chromosphere. We analyzed the multiline Stokes profiles of the photospheric Fe i and K i lines and the chromospheric Ca ii lines, and applied the weak field approximation to the K i and Ca ii lines to reconstruct the 3D magnetic field structure. The blue- and red-wing brightenings of the Ca ii 8542 Å line appear at spatially offset locations, indicating bidirectional reconnection flows. The reconstructed 3D magnetic field reveals that the opposite-polarity field structure reaches different heights in the two events analyzed. In one event, it is confined to the lower layers and is absent at the formation height of the Ca ii 8542 Å core, which shows no intensity enhancement, whereas in the other event it extends up to the Ca ii 8542 Å core formation height, where enhanced line-core intensity is also observed. We interpret this as the reconnection current sheet reaching different altitudes. These results demonstrate that SCIP has successfully resolved the 3D structure of EBs, distinguishing magnetic reconnection events occurring at different atmospheric heights.

We report high-spatial-resolution spectropolarimetric observations spatially associated with a solar filament, obtained with the S unrise Chromospheric Infrared Spectro-Polarimeter (SCIP) on board the S unrise iii balloon-borne solar observatory on 2024 July 15. The observed filament was located near the solar disk center, adjacent to an active region, and remained quiescent for at least 2 hr during the observing period. SCIP recorded full Stokes profiles in the Ca ii 8542 Å line, revealing clear signatures of linear polarization produced by the transverse Zeeman effect. The detected linear polarization signals within the filament region exceeded the 2 σ noise level and exhibited a characteristic Zeeman double-lobe spectral shape that distinguishes them from polarization due to scattering. The magnetic field strength derived using the weak field approximation is approximately −80 G along the line of sight and 300–500 G in the transverse direction. These values likely reflect the magnetic properties of the filament and its supporting chromospheric environment. The orientation of the magnetic field vector is nearly parallel to the filament axis in its northeastern portion, while the southeastern part of the filament extends outside the field of view. To our knowledge, this is the first unambiguous detection of linear polarization associated with a solar filament with the Ca ii 8542 Å line. Our results open a new diagnostic window to the vector magnetic structure of solar filaments in the lower chromosphere, complementing existing He i based diagnostics that probe the upper chromosphere.

The balloon-borne stratospheric solar observatory Sunrise III successfully completed 6.5 days of observations in July 2024. One of its focal-plane instruments, the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP), is a slit-scanning spectropolarimeter that simultaneously measures full Stokes profiles of multiple spectral lines in the 850 nm and 770 nm bands. SCIP obtained an unprecedented data set of a quiet-sun region near disk center, covering a 58”× 58” field of view. With an integration time of 10 s per slit position, the scan was completed in 107 minutes without interruption, achieving remarkably stable polarimetric precision of 0.03-0.04

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.

Understanding the magnetic field structure of spicules is essential for developing their formation models, which are important for understanding the mass transport to the corona and coronal heating. We report the spatial distribution of spicule magnetic fields from spectropolarimetric observations with Sunrise iii /SCIP, which provides high spatial resolution and high polarization sensitivity under seeing-free conditions. We observed the solar limb above a quiet region with SCIP and detected clear Stokes V signals in the Ca II 8542 Å line from off-limb spicules. We applied the weak field approximation to estimate the line-of-sight (LOS) component of the magnetic field ( B _LOS ) of spicules. We find that B _LOS ranges up to 20 G, nearly independent of height, in the region up to 3″ from the limb, whereas the distribution broadens to 40 G at 3″–6″ from the limb. The Stokes I profiles averaged at increasing distance from the limb reveal a transition from a double-peaked shape to a single-peaked one at around 3″ from the limb. Because we can see a dense forest of spicules overlapping each other above the limb, the observational results suggest that the B _LOS depends on how deeply the Ca II line can penetrate the spicule forest along the LOS. At heights with double-peaked profiles, the estimated B _LOS represents the magnetic field of a foreground spicule. In contrast, at heights with single-peaked profiles, it reflects contributions from a number of prominent, tall, inclined spicules, leading to more dispersed B _LOS values.

Ellerman bombs (EBs) are widely recognized as photospheric and chromospheric signatures of magnetic reconnection. However, the three-dimensional (3D) magnetic topology has remained elusive due to the lack of seamless height coverage in observations. Here, we present initial results from the SUNRISE III/SCIP (Sunrise Chromospheric Infrared spectroPolarimeter) observations of an emerging flux region. Exploiting the seeing-free, high-spatial-resolution observations provided by the 1-meter balloon-borne telescope, SCIP achieved seamless multi-line spectropolarimetry from the photosphere to the lower chromosphere. We analyzed the multi-line Stokes profiles of the photospheric Fe I and K I lines and the chromospheric Ca II lines, and applied the Weak Field Approximation to the K I and Ca II lines to reconstruct the 3D magnetic field structure. The blue- and red-wing brightenings of the Ca II 8542 Å line appear at spatially offset locations, indicating bi-directional reconnection flows. The reconstructed 3D magnetic field reveals that the opposite-polarity field structure reaches different heights in the two events analyzed. In one event, it is confined to the lower layers and is absent at the formation height of Ca II 8542 Å core, which shows no intensity enhancement, whereas in the other event it extends up to the Ca II 8542 Å core formation height, where enhanced line-core intensity is also observed. We interpret this as the reconnection current sheet reaching different altitudes. These results demonstrate that SCIP has successfully resolved the 3D structure of EBs, distinguishing magnetic reconnection events occurring at different atmospheric heights.

A part of the magnetic energy released during a flare is transported to the lower atmosphere. High-resolution observations show that flare ribbons, sites of energy deposition at the footpoints of flaring loops that appear bright in the chromosphere and transition region, are structured on small spatial scales on the order of 100 km. Based on idealized numerical models of flares it is suggested that the ribbon fine structures could originate from a tearing instability and the development of plasmoids in current sheets. Here we report on Fe i 5250.6 Å and Mg i b _2 5173 Å spectral observations of a solar flare from the Tunable Magnetograph on board the S unrise iii balloon-borne mission that reveal an intricate link between the flare ribbon structure and the ambient chromosphere. We identified uncombed chromospheric loops and nonflaring fine structures that are interspersed among brighter flare ribbon threads. These loops remain stable on timescales of minutes. Spectral lines from these regions show reduced emission or self-reversal in the line core compared with the immediately adjacent flare ribbons. We discuss the potential role of these structures in the onset of a flare. Furthermore, we suggest that irrespective of the complexities in the flaring current sheet, uncombed chromospheric loops and nonflaring fine structure might play a role in spatially modulating the flare energy deposition in the lower atmosphere.

Sunrise III is a stratospheric balloon-borne solar observatory with a 1-m diameter telescope and three post-focus instruments, along with an image stabilisation system, all within a protective gondola. It samples the lower solar atmosphere, from the solar surface to the middle chromosphere, at a resolution approaching 50 km on the Sun. Sunrise III flew successfully for 6.5 days suspended from a zero-pressure stratospheric balloon from northern Sweden to north-western Canada in July 2024, gathering around 200 TB of data. The present issue of ApJL focuses on the first scientific results from the data collected during that flight. This paper introduces this Focus Issue, providing a very brief overview of the capabilities of the instrumentation, the flight and of the gathered data. Challenges for the measurements, data reduction and interpretation are also briefly touched upon. The paper ends with an overview of the first set of science results obtained from these data, as presented in the current Focus Issue.

Magnetohydrodynamic waves redistribute energy in magnetic structures of the lower solar atmosphere, yet constraints on how wave power and dominant frequencies are organised 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-UV spectroscopy with the Sunrise-III UV Spectropolarimeter and Imager (SUSI). We analyse a two-hour time series of repeated raster scans of a sunspot near disc centre 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 deep photosphere toward the low chromosphere. For each line, we extract line-core intensity and line-of-sight velocity time series using a dedicated multi-line fitting routine and compute Morlet-wavelet power spectra. The refined global wavelet spectra show that most lines (in both intensity and velocity) are genuinely multi-frequency, with a dominant peak and substantial statistically significant power up to 12 mHz. Unsupervised clustering of the normalised 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 behaviour 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 Sunrise-III/SUSI observations open a new regime for near-UV multi-line wave studies and provide the first systematic characterisation of frequency-structured sunspot wave behaviour in this spectral region.

Acoustic waves propagate into the chromosphere, contributing to energy transport and their dynamics. Their upward propagation is restricted to frequencies above the acoustic cutoff frequency. The magnetic field configuration plays a key role in determining whether acoustic waves can propagate upward because the cutoff frequency is reduced in regions where the field is inclined with respect to gravity, forming so-called magnetoacoustic portals. Previous studies linked magnetic fields and oscillations in quiet regions, but these analyses were based on photospheric magnetic field information, leaving chromospheric structure unconstrained. This study investigates the coupling between acoustic waves and magnetic topology using photospheric and, for the first time, chromospheric spectropolarimetry in a quiet region, obtained with the Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP) aboard the Sunrise iii balloon-borne solar observatory launched in 2024. The SCIP sit-and-stare observations sampled magnetic features in which the line-of-sight field strength exhibits multiple sharp spatial peaks in the photosphere while becoming broader and weaker at two heights in the chromosphere, indicating expanding fluxtubes. The chromospheric velocity field in these fluxtubes exhibits strong 5-minute oscillations, while the surrounding regions show weak 3-minute oscillations. In these fluxtubes, sawtooth temporal velocity variations are associated with intensity enhancements, suggesting steepened shocks. Fluxtubes with low-frequency oscillations are identified not only in network regions but also in weak internetwork regions. These results provide observational evidence that fluxtubes expanding into the chromosphere act as magnetoacoustic portals, in both network and internetwork regions, allowing low-frequency waves to propagate upward and driving chromospheric dynamics via shocks.

We report on the measurement of the height-dependent time shifts of wave pulses in the lower solar atmosphere from high-resolution spectro-polarimetric observations obtained with the SUSI instrument on board the SUNRISE III balloon-borne solar observatory during its successful science flight in July 2024. The line-of-sight velocities derived from the line-core positions of 19 spectral lines in a 2 nm-wide window around the Ca II H line were used to determine the time shifts of propagating pulses at their respective formation heights. Our analysis reveals that these shifts are roughly ordered according to the computed formation heights of the respective spectral lines. A statistical analysis of the time shifts using sit-and-stare observations with a total duration of one hour reveals that wave pulses propagating upwards from near the solar surface to heights of approximately 500-700 km are most common, with average time lags of 20 s to 30 s between these heights. Also present are pulses with close-to-zero phase shifts, predominantly above intergranular lanes and areas of enhanced magnetic activity. Additionally, downward propagating wave pulses with negative time lags of 10 s to 15 s are seen, mostly above areas of enhanced magnetic activity. A common feature of all the observed pulses is that in the lower 250 km they show small time lags of zero to a few seconds, and only at higher layers do the propagating pulses become more dominant. This study demonstrates the potential of the many-line approach for investigating the height dependence of the physical conditions in the solar atmosphere.

We report the detection of high-order hydrogen Paschen emission lines (Pa 15, Pa 16, and Pa 17) in the quiet-Sun chromosphere off the solar limb using the Chromospheric Infrared SpectroPolarimeter (SCIP) on board the Sunrise iii balloon telescope. These lines reveal thread-like structures resembling spicules and exhibit systematically smaller Doppler velocities than Ca II 854.2 nm, suggesting that they are optically thinner and more affected by line-of-sight averaging, especially near the limb. Non-LTE radiative transfer synthesis using the spherically symmetric one-dimensional code reproduces the overall spectral properties. The observed ratios among three Paschen lines show systematic deviations from synthetic and theoretical results, suggesting that additional physical effects may influence the formation of high-order Paschen lines. The study demonstrates the potential of high-order Paschen lines as a new diagnostic of optically thin plasma in the off-limb chromosphere.

We present high-resolution multi-line spectropolarimetric observations of a quiet-Sun network element obtained with the Sunrise 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 polarisation is concentrated in a narrow ridge around the edge of the magnetic element, co-spatial with enhanced transverse magnetic field inferred from multiline inversions. The magnetic azimuth exhibits a coherent, predominantly radial organisation 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 polarisation reproduces the same large-scale organisation, 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 polarisation is sensitive to magnetic azimuth in the upper photosphere, with the closest proxy agreement occurring near ≈-3. We find no evidence for strong azimuthal shear between the Fe- and K-sensitive diagnostics. At the network boundary, we also identify localised parasitic-polarity patches associated with complex, multi-lobed 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 organised upper-photospheric canopy fields together with small-scale mixed-polarity structure, providing new constraints on the three-dimensional magnetic structure of network elements.