Sarah Elizabeth Gibson

Two-dimensional (2D) coronal seismology based on coronagraphic imaging spectroscopy has emerged as a promising method for mapping the coronal magnetic field, but the physical meaning of its inferred quantities under optically thin line-of-sight (LOS) integration remains uncertain. We investigate this problem by synthesizing coronagraphic observables from a global wave-driven magnetohydrodynamic model with a long LOS extent and a structured corona and by applying the same analysis procedures used for observations. We compare the diagnosed density, wave propagation direction, phase speed, and magnetic-field strength with different LOS-weighted reference quantities from the model. We find that the measured density and the wave propagation direction are both well represented by LOS emissivity-weighted quantities. In contrast, the phase speed is not controlled by emissivity weighting alone: the LOS distribution of wave velocity amplitude also plays an important role. As a result, the inferred magnetic field is better represented by combining the emissivity-weighted density with an amplitude-dependent effective speed. Emissivity weighting nevertheless remains a reasonable approximation, and a useful baseline, over much of the field of view, especially where the LOS does not cross strongly structured plasma-sheet-like regions. These results clarify the physical interpretation of 2D coronal seismology and provide guidance for future coronal magnetic-field tomography and model-constrained applications.

Coronal cavities are low-density regions in the solar corona surrounding prominences that often erupt into coronal mass ejections. Therefore, understanding the magnetic field in these preeruptive structures is important for understanding the process of magnetic energy storage and release in the solar corona, with implications for space weather modeling and predictions. The Daniel K. Inouye Solar Telescope/CryoNIRSP instrument acquired spectropolarimetric observations of the Fe xiii 10747 Å forbidden emission line in two coronal cavities, one on the northwest limb on 2025 August 8 and the other on the southwest limb on 2025 October 5. For the first time, we detect the circularly polarized emission in the Stokes V parameter in the coronal cavities and their embedded structures, which could be resolved such that the line-of-sight (LOS) magnetic field intensity could be estimated using the weak-field approximation. It is found that the inferred LOS magnetic field strength varies from ∼5 to 20 G in the cavity, with the strongest field strength above the prominence in the hornlike substructure of the cavity.

Coronal prominences are involved in many coronal mass ejections (CMEs), but the prominence traces only a portion of the 3D magnetic field of the core of the CME. The cavities surrounding them encompass much larger volumes, making them ideal candidates for studying preeruption magnetic structures. We present a new survey of >3500 coronal prominence cavities that span the solar cycle, including solar maximum, declining phase, and solar minimum. The survey includes cavities observed in the extreme-ultraviolet (Solar Dynamics Observatory Atmospheric Imaging Assembly). For all of the cavities, we determined the parameters that define their position and size and showed how the frequency of occurrence and the position of the cavities change with the solar cycle.

Atmospheric aerosols strongly influence daytime sky quality for solar coronal imaging, yet few studies directly link aerosol properties and sky brightness measurements within ∼2° of the Sun. Here, we compare externally occulted coronagraphic measurements of near-Sun radiance with aerosol-constrained inferences derived from direct-Sun and sky photometry. Our analysis focuses on Mauna Loa Observatory, a well-characterized high-altitude site for atmospheric and solar observations. We present coronagraphic measurements of near-Sun radiance at 1 . ° 54 ± 0 . ° 77 from the solar disk center acquired between 2006 and 2007 by an ATST sky brightness monitor (SBM). These data are directly compared with circumsolar radiances inferred at 1 . ° 54 using Aerosol Robotic Network (AERONET) almucantar measurements and aerosol optical retrievals. We find quantitative agreement between these two approaches, enabling extension to multidecadal analyses of circumsolar radiance and its relationship to aerosol properties and related proxies (e.g., the Ångström exponent) using AERONET data from 2000 to 2025. Near-Sun radiances are expressed relative to the solar disk-center radiance, facilitating direct comparison to related studies. Finally, we synthesize physically based true-color images of the circumsolar sky under representative aerosol conditions as an observational aid, in part to illustrate that visually enhanced solar aureoles do not necessarily imply poor infrared coronal observing conditions. This methodology provides an extended framework for assessing daytime coronal sky quality at existing and future observing sites, including DKIST and the proposed Coronal Solar Magnetism Observatory facility.

The origin of the slow solar wind remains a subject of ongoing debate. Several mechanisms have been proposed: the large expansion factor of open magnetic field in the corona, interchange reconnection between open and closed field lines in streamers and pseudostreamers, reconnection within the web of separatrices (S-web), and the field line pinch-off at streamer cusps. Many of these mechanisms involve the release of small-scale density inhomogeneities into the solar wind. A significant obstacle to understanding these processes is the difficulty of observing the region between the lower corona (traditionally observed with extreme ultraviolet imagers) and the high corona (traditionally observed with externally occulted coronagraphs), where these small-scale structures are thought to originate. Here, we present for the first time high-cadence (30 s) and high-spatial-resolution (5 . ″ 6) white-light observations of the solar corona in the range of the radial distances r of 1.1 R _⊙ < r < 3 R _⊙ taken by the ASPIICS coronagraph on board the formation-flying Proba-3 mission. The ASPIICS data reveal ubiquitous, weak (0.5%–2% of the background brightness), small-scale dynamic features (blobs, outflows, inflows, jets, and waves). Their speeds range from 14 km s ⁻¹ to 520 km s ⁻¹ , with outflowing structures generally propagating faster than the inflowing ones. All these features appear to originate from streamers and pseudostreamers. ASPIICS observations provide important constraints on the role of small-scale dynamics in the formation of the slow solar wind.

The ratio of radially to tangentially polarized Thomson-scattered white light provides a powerful tool for locating the 3D position of compact structures in the solar corona and inner heliosphere, and the Polarimeter to Unify the Corona and Heliosphere (PUNCH) has been designed to take full advantage of this diagnostic capability. Interestingly, this same observable that establishes the position of transient blob-like structures becomes a local measure of the slope of the global falloff of density in the background solar wind. It is thus important to characterize the extent along the line of sight of structures being studied, in order to determine whether they are sufficiently compact for 3D positioning. In this paper, we build from analyses of individual lines of sight to three-dimensional models of coronal mass ejections (CMEs), allowing us to consider how accurately polarization properties of the transient and quiescent solar wind are diagnosed. In this way, we demonstrate the challenges and opportunities presented by PUNCH polarization data for various quantitative diagnostics.

In recent years, a two-dimensional (2D) coronal seismology technique applied to spectral-imaging data from the Coronal Multi-channel Polarimeter (CoMP) and Upgraded Coronal Multi-channel Polarimeter (UCoMP) has enabled routine measurement of the global coronal magnetic field. The technique combines coronal transverse wave phase speed from Doppler measurements with electron densities from the Fe xiii 10798/10747 Å intensity ratio to infer the magnetic field strength, while the wave propagation directions from Doppler measurements trace the magnetic field direction. To validate the accuracy and robustness of this method, we use forward modeling of a MURaM simulation that produces open and closed magnetic structures with excited waves. From the synthetic Doppler velocity, Fe xiii infrared line intensities, and linear polarization signals, we apply the 2D coronal seismology technique to estimate the magnetic field strength and direction. A comparison with the simulation ground truth shows close agreement, indicating that the technique can recover the line-of-sight (LOS) emissivity-weighted magnetic field direction and strength with high accuracy. We also perform a parameter-space analysis to quantify the sensitivities of the method to parameter choice. These findings provide practical guidance for CoMP/UCoMP-like analysis and demonstrate that 2D coronal seismology can deliver reliable, LOS emissivity-weighted measurements of the coronal magnetic field from coronal wave observations.

The Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission is a NASA Small Explorer to determine the cross-scale processes that unify the solar corona and heliosphere. PUNCH has two science objectives: (1) understand how coronal structures become the ambient solar wind, and (2) understand the dynamic evolution of transient structures, such as coronal mass ejections, in the young solar wind. To address these objectives, PUNCH uses a constellation of four small spacecraft in Sun-synchronous low Earth orbit, to collect linearly polarized images of the K corona and young solar wind. The four spacecraft each carry one visible-light imager in a 1 + 3 configuration: a single Narrow Field Imager solar coronagraph captures images of the outer corona at all position angles, and at solar elongations from 1.5° (6 R _⊙ ) to 8° (32 R _⊙ ); and three separate Wide Field Imager heliospheric imagers together capture views of the entire inner solar system, at solar elongations from 3° (12 R _⊙ ) to 45° (180 R _⊙ ) from the Sun. PUNCH images include linear-polarization data, to enable inferring the three-dimensional structure of visible features without stereoscopy. The instruments are matched in wavelength passband, support overlapping instantaneous fields of view, and are operated synchronously, to act as a single “virtual instrument” with a 90 ^∘ wide field of view, centered on the Sun. PUNCH launched in March of 2025 and began science operations in June of 2025. PUNCH has an open data policy with no proprietary period, and PUNCH Science Team Meetings are open to all.

The recently launched PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission has unprecedented capabilities to image the evolving solar wind from the outer corona into the heliosphere. The data provided by PUNCH offers a unique opportunity to investigate the solar wind structures across multiple scales. In this work, we present a preliminary analysis of PUNCH flow data and its potential applications to the SynCOM (Synthetic Corona Outflow Model) framework, which simulates solar wind outflows driven by empirical constraints.

Variations of the magnetic field within a solar coronal mass ejection (CME) in the heliosphere depend on the CME’s magnetic structure as it leaves the solar corona and its interplanetary evolution. To account for this evolution, we developed a new numerical model of the inner heliosphere that simulates the propagation of a CME through a realistic solar wind background and allows various CME magnetic topologies. To this end, we incorporate the Gibson–Low CME model within our global MHD model of the inner heliosphere, GAMERA-Helio. We apply the model to study the propagation of the geoeffective CME that erupted on 2010 April 3, aiming to reproduce the temporal variations of the magnetic field vector during the CME’s passage by Earth. Parameters of the Gibson–Low CME are informed by STEREO white-light observations near the Sun. The magnetic topology for this CME—the tethered flux rope—is informed by in situ magnetic field observations near Earth. We performed two simulations testing different CME propagation directions. For an in-ecliptic direction, the simulation shows a rotation of all three magnetic field components within the CME, as seen at Earth, similar to that observed. However, the magnitudes of the components, particularly at the back of the CME, are underestimated by the model. With a southward direction, suggested by coronal imaging observations, the B _x component lacks the observed change from negative to positive. In both cases, the model favors the east–west orientation of the flux rope, consistent with the orientation previously inferred from the images from STEREO/Heliospheric Imager.