Shadia Rifai Habbal

We report on the first inference of the nonthermal energy flux and subsequent heating across the prominence–corona transition region (PCTR) and a nearby active region (NOAA AR 13875) using DKIST/Cryo-NIRSP spectropolarimetric measurements. The observations were acquired on 2024 October 20 and 21, in the Fe xiii 1074.7 and 1079.8 nm lines as well as in He i 1083 nm. The nonthermal component of the Gaussian line broadening was extracted from the Fe xiii 1074.7 nm observations, assuming a locally isothermal plasma. Electron density was inferred from the Fe xiii 1079.8 nm/1074.7 nm line ratio. The full Stokes polarimetry enabled the modeling of a partial coronal magnetogram, which offered constraints on an empirical model to infer magnetic field strength. The inferred density, nonthermal line widths, and magnetic field strength enabled the calculation of wave energy density, Alfvén velocity, Alfvén energy flux, and volumetric heating rates in the target region. The prominence shroud appeared as a narrow and highly dynamic layer between the prominence and the overlying cavity. Each structure exhibited a different exponential volumetric heating decay rate as a function of coronal height, with e-folding length scales of 9.1 ± 1.9 Mm, 58.1 ± 5.4 Mm, and 45.1 ± 2.9 Mm, respectively, in the PCTR, overlying cavity, and nearby AR. Additionally, we found that the prominence exhibits phase-shifted, wavelike velocity and intensity structures in the He i 1083 nm line, suggesting magnetoacoustic waves may be responsible for damping and local heating around the PCTR.

Characterizing the sources and dynamics of solar-wind streams is challenging given the complexity of the magnetized density structures and the absence of speed measurements in the low corona. White-light (WL) coronagraphic observations from the recently launched Proba-3/ASPIICS mission now offer the first opportunity to capture the dynamics of WL coronal structures over an uninterrupted span between 1.2 and 3 R _⊙ over a period of several hours. In this Letter, we use a 5 minute time-differenced wavelet-optimized whitening technique to measure apparent motions of WL density structures in the corona using features measured in height–time plots. These height–time plots are subsequently enhanced using a technique similar to the principle of multiscale Gaussian normalization to automate the detection of these features to produce plane-of-sky apparent speed maps. Application of this technique to the Proba-3/ASPIICS data acquired on 2025 July 16 revealed the presence of outflows, as well as inflows, with average speeds of 100 and −50 km s ⁻¹ , respectively. The speed of a coronal mass ejection (CME), its leading edge and its fine scale substructures, which were clearly visible within the field of view, could also be measured. These first apparent speed maps of coronal density structures highlight the currently unsurpassed effectiveness of the Proba-3 mission for the exploration of the origin and evolution of the solar wind. They also provide novel boundary conditions for two- and three-dimensional models of the dynamic corona.

Turbulence is a fundamental process in astrophysical plasmas, playing a key role in energy transfer and dissipation. The solar corona is thought to be heated to temperatures exceeding 10 ⁶ K in part by turbulent processes. Using the highest-resolution white-light total solar eclipse image obtained during the 2017 August 21 eclipse, we present quantitative constraints on anisotropic turbulent structuring in the solar corona below a heliocentric distance of 1.4 R _⊙ . We compute power spectra in ∼0.4 R _⊙ wide square subregions extending outward from the solar surface, separating observed structures into three magnetic categories: closed-field, open-field, and mixed magnetic field regions. Spectral slopes are measured separately along directions parallel and perpendicular to the principal axes of the observed anisotropy in k -space. Comparing closed- to open-field regions, we observe a systematic steepening in the k _⊥ spectra, a comparatively consistent k _∥ spectra, and an increase in anisotropy with decreasing complexity in magnetic topology. These results are consistent with a quasi-2D plus slab organization of coronal fluctuations, in which the k _⊥ spectra primarily reflect quasi-two-dimensional structuring, while the k _∥ spectra are dominated by field-aligned, slab-like fluctuations. The comparison of these spectra across different magnetic topologies provides evidence for developing anisotropic turbulence within 0.4 R _⊙ of the solar surface.

High-resolution total solar eclipse (TSE) white light (WL) images are the only observations at present to capture coronal structures over an uninterrupted field of view (FoV) of at least 10 solar radii ( R _s ) starting from the solar limb. They were the first to report the presence of vortex rings originating within the prominence–corona transition region (PCTR). They have also captured coronal mass ejections (CMEs) and Kelvin–Helmholtz (KH) instabilities at different phases of their evolution. While the evolution of CMEs and KH waves is relatively well documented, little is known about the survivability of vortex rings beyond the FoV of TSE images. In this study, we use seven TSE images and noncontemporaneous WL images acquired by the Wide-field Imager for Parker Solar Probe (WISPR) to track the spatial evolution of vortex rings, KH waves, and CMEs. The size trend versus radial distance for vortex rings and KH waves is found to be shallower below 1.5 R _s than beyond 3 R _s , while the CMEs observed beyond 3 R _s show a unique slope. The WISPR time series yields an average speed of 249.02 ± 25.3 km s ⁻¹ for the vortex rings beyond 3 R _s , which when combined with their size yields a speed of 19.39 ± 3.20 km s ⁻¹ below 1 R _s . These values are remarkably consistent with the acceleration profile of the slow solar wind over the same distance. This study provides strong empirical evidence that vortex rings, which originate at the PCTR with complex magnetic structures, do not dissipate as they expand away from the Sun with the solar wind.

We present narrowband observations of the Fe xiv (530.3 nm), Fe x (637.4 nm), and Fe xi (789.2 nm) coronal emission lines from the 2023 April 20 Total Solar Eclipse in Australia. We deployed pairs of telescopes for each emission line that were equipped with narrowband filters centered on, and several nanometers away from, the center wavelengths of the lines. The secondary continuum telescopes were used to measure and remove the combined continuum K- (electron) and F- (dust) corona, which dominate coronal emission at optical and infrared wavelengths. Significant emission was detected from all three lines from 1.03 solar radii ( R _⊙ ) continuously outward to at least 6 R _⊙ . The brightness of the lines and continuum are absolutely calibrated to the solar disk, and are validated by a comparison with LASCO-C2 observations made at the same time. Using these observations, we inferred the line emission ratios resolved throughout the middle-corona (defined as 1.5–6 R _⊙ ) for the first time. These line ratios are a probe of the electron temperature, which have important implications for constraining models of coronal heating and the characterization of solar wind formation, yet these emission lines have scarcely been quantified beyond 3 R _⊙ in the corona. This study demonstrates the enduring potential of eclipse observations for coronal physics and suggests that future spacecraft missions could observe these lines farther out than has been attempted previously.

High-resolution total solar eclipse (TSE) white light (WL) images are the only observations at present to capture coronal structures over an uninterrupted field of view (FoV) of at least 10 solar radii (Rs) starting from the solar limb. They were the first to report the presence of vortex rings originating within the prominence-corona transition region (PCTR). They also captured CMEs and Kelvin-Helmholtz (KH) instabilities at different phases of their evolution. While the evolution of CMEs and KH waves is relatively well-documented, little is known about the survivability of vortex rings beyond the FoV of the TSE images. In this study, we use seven TSE images and non-contemporaneous WL images acquired by the Wide-Field Imager for Parker Solar PRobe (WISPR) to track the spatial evolution of vortex rings, KH waves, and CMEs. The size trend versus radial distance for vortex rings and KH waves are found to be shallower below 1.5 Rs than beyond 3 Rs, while the CMEs observed beyond 3 Rs show a unique slope. The WISPR time series yield an average speed of 249.02 +/- 25.3 km/s for the vortex rings beyond 3 Rs, that when combined with their size yields a speed of 19.39 +/- 3.20 km/s below 1 Rs. These values are remarkably consistent with the acceleration profile of the slow solar wind over the same distance. This study provides strong empirical evidence that vortex rings, which originate at the PCTR with complex magnetic structures, do not dissipate as they expand away from the Sun with the solar wind.

We present narrowband observations of the Fe XIV (530.3 nm), Fe X (637.4 nm), and Fe XI (789.2 nm) coronal emission lines from the 2023 April 20 Total Solar Eclipse in Australia. We deployed pairs of telescopes for each emission line that were equipped with narrowband filters centered on, and several nanometers away from, the center wavelengths of the lines. The secondary continuum telescopes were used to measure and remove the combined continuum K- (electron) and F- (dust) corona, which dominate coronal emission at optical and infrared wavelengths. Significant emission was detected from all three lines from 1.03 solar radii (Rs) continuously outward to at least 6 Rs. The brightness of the lines and continuum are absolutely calibrated to the solar disk, and are validated by a comparison with LASCO-C2 observations made at the same time. Using these observations, we inferred the line emission ratios resolved throughout the middle-corona (defined as 1.5 to 6 Rs) for the first time. These line ratios are a probe of the electron temperature, which have important implications for constraining models of coronal heating and the characterization of solar wind formation, yet these emission lines have scarcely been quantified beyond 3 Rs in the corona. This study demonstrates the enduring potential of eclipse observations for coronal physics and suggests that future spacecraft missions could observe these lines farther out than has been attempted previously.

We report in this Letter on the first use of a kite as an airborne platform for coronal observations during total solar eclipses, to mitigate the detrimental impact of clouds when present. In this first innovative attempt, the scientific payload was chosen to be a single-channel color spectrometer operating in high order over the wavelength range of 400–1000 nm, with light being fed from a coelostat that tracked the Sun optically. The payload was made airborne by a Cody-box-type kite with a wingspan of 6.5 m and launched from Cape Range National Park in North West Australia during the 2023 April 20 total solar eclipse. The kite and payload reached a terminal altitude of 450 m about 30 minutes prior to second contact and remained airborne 1 hr past the 58 s of totality. Although the tracking was not perfect, it nevertheless enabled the acquisition of two coronal spectra. This first successful technology demonstration paves the way for the feasibility of future low-cost kite-borne payloads for astronomical observations not limited to total solar eclipses.

The solar atmosphere displays a sharp temperature gradient, starting from spicules in the chromosphere at 2 × 10⁴ K, outward into the corona exceeding 10 6 K. Plasma turbulence produced by the transverse motion of magnetic fields anchored in the photosphere is likely the energy source producing this gradient. However, very little is known about the turbulent structures near the solar surface. Using the highest spatial resolution white-light total solar eclipse image to date, we measure the transverse correlation length at distances ranging from 0.33 to 94 Mm above the solar surface—2 orders of magnitude closer than previous estimates. Our results show that the turbulence injection scale in the chromosphere is ∼1.5 Mm, which we associate with the size of granules since they are the only structured features of comparable size. Further, the change in perpendicular correlation length with distance from the solar surface exhibits a plateau in the first 4 Mm, followed by a rapid increase until 9 Mm where it becomes shallower thereafter. We associate this radial gradient with the expansion of the magnetic field in the transition region between the chromosphere and the corona.