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Abstract 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 10⁶ 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 ink-space. Comparing closed- to open-field regions, we observe a systematic steepening in thek_⊥spectra, a comparatively consistentk_∥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 thek_⊥spectra primarily reflect quasi-two-dimensional structuring, while thek_∥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. 

Abstract 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 1.5R_sthan beyond 3R_s, while the CMEs observed beyond 3R_sshow a unique slope. The WISPR time series yields an average speed of 249.02 ± 25.3 km s⁻¹for the vortex rings beyond 3R_s, which when combined with their size yields a speed of 19.39 ± 3.20 km s⁻¹below 1R_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. 

Abstract Coronal mass ejections (CMEs), as seen in white-light (WL) coronagraphs, often exhibit a classic three-part structure consisting of a bright front, a dark cavity, and a bright core. With the launch of Solar Orbiter, cospatial imaging of solar eruptions in multiwavelengths of extreme-ultraviolet (EUV) and WL has become available. We present a CME that erupted on 2022 September 23, observed under a uniquely favorable viewing geometry. The CME bright core and its eruptive prominence can be cospatially observed up to a coronal height of 3.5R_⊙in the middle corona, in WL using COR1 on board STEREO-A and in EUV using the Full Sun Imager on board Solar Orbiter. Cospatial, multiwavelength observations indicate that the CME bright core observed in WL was almost entirely composed of the prominence material, which was heated during the CME eruption. EUV emissions in 174 and 304 Å of the prominence were largely cospatial when the CME propagated to the middle corona, though subtle differences remained. We further discuss the potential temperature in the bright core region and find that the core was heated as it rose, likely reaching temperatures of about 0.1–0.8 MK. 

Abstract Understanding the location and evolution of the cool dense prominence in relation to the large-scale structure of coronal mass ejections (CMEs) is critical to distinguish between different CME initiation mechanisms and to further deepen our understanding of CME evolution through the heliosphere. Combining remote observations of extreme-ultraviolet images and white-light coronagraphs and heliospheric imagers (HIs) obtained from the Solar Dynamics Observatory, Solar and Heliospheric Observatory, STEREO-A, and Solar Orbiter, we present an analysis of the continuous tracking from the corona to interplanetary space of the substructures of a CME associated with a prominence that erupted on 2022 September 23. The prominence is found to remain bright and compact during the CME propagation for more than three days. We investigate the kinematic evolution of the CME substructures as the CME propagated to around 0.5 au. We find that for the first 0.28 au, both the CME front and prominence propagated coherently, indicating that the prominence was tied to the CME magnetic structure. Beyond 0.28 au, the CME bright front was seen to be distorted. However, the prominence continued to propagate at a nearly constant velocity up to at least 0.5 au. STEREO-A/HI images further show a dark ridge-like feature trailing the CME that passed over the prominence, and the prominence appeared tilted. We deduce that the prominence propagated independently of the CME at larger distances from the Sun. Overall, this study shows that both previously proposed hypotheses—namely, that the prominence is tied to or propagates independently of the CME—are valid but within different distance ranges. 

The electron density of the solar corona is a fundamental parameter in many areas of solar physics. Traditionally, routine estimates of coronal density have relied exclusively on white-light observations. However, these density estimates, obtained by inverting the white-light data, require simplifying assumptions, which may affect the robustness of the measurements. Hence, to improve the reliability of coronal density measurements, it is highly desirable to explore other complementary methods. In this study, we estimate the coronal electron densities in the middle corona, between approximately 1.7 and 3.5R_⊙, using low-frequency radio observations from the recently commissioned Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA). The results demonstrate consistency with those derived from white-light coronagraph data and predictions from theoretical models. We also derive a density model valid between 1.7 and 3.5r_⊙, given by $\rho \left(r^{\prime }\right)=1.27{r{}^{\prime }}^{-2}+29.02{r{}^{\prime }}^{-4}+71.18{r{}^{\prime }}^{-6}$, where $r^{\prime }=r/R_{\odot }$, withrthe heliocentric distance. OVRO-LWA is a solar-dedicated radio interferometer that provides science-ready images with low latency, making it well suited for generating regular and independent estimates of coronal densities to complement existing white-light techniques. 

This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere.