Elena Provornikova

Coronagraphic observations enable direct monitoring of coronal mass ejections (CMEs) through scattered light from free electrons, but determining the 3D plasma distribution from 2D imaging data is challenging due to the optically thin plasma and the complex image formation. We introduce Sun Neural Radiance Field for CMEs (SuNeRF-CME), a framework for 3D tomographic reconstructions of the heliosphere using multiviewpoint coronagraphic observations. The method uses a neural radiance-field to estimate the electron density in the heliosphere through ray tracing, while accounting for the underlying Thomson scattering. The model is optimized by iteratively fitting the time-dependent observational data. In addition, we apply physical constraints in terms of continuity, propagation direction, and speed of the heliospheric plasma to overcome limitations imposed by the sparse number of viewpoints. We utilize synthetic observations of a CME simulation to quantify the model’s performance for different viewpoint configurations. Within this controlled synthetic setting, the results demonstrate that our method can reliably estimate the CME parameters from only two viewpoints, with a mean velocity error of 3.01% ± 1.94% and propagation direction errors of 3 . ° 39 ± 1 . ° 94 in latitude and 1 . ° 76 ± 0 . ° 79 in longitude. We further show that our approach can achieve a 3D reconstruction of the simulated CME from two viewpoints, where we correctly model the three-part structure, deformed CME front, and internal plasma variations. Additional viewpoints can be seamlessly integrated, directly enhancing the reconstruction of the plasma distribution in the heliosphere. These results demonstrate the potential of physics-informed radiance-field methods for CME tomography, paving the way for future extensions toward observational data and space weather applications.

We present a community effort to assess how open science can advance heliophysics and space weather modeling. Open science has the potential to enhance the quality and pace of scientific discovery, but its application to scientific modeling requires more careful consideration with respect to open data and open software guidelines, as complex scientific models are not ordinary software. We gathered feedback from modeling teams worldwide through a living survey and discussion sessions at the Open Science Workshop in College Park, USA, in 2024, and the COSPAR ISWAT Initiative Working Meeting in Cape Canaveral, USA, in 2025. We complement these findings with lessons learned from almost 25 years of experience at the Community Coordinated Modeling Center in enabling open use of models. We identify key roadblocks in current open science practices and guidelines and offer recommendations for future progress. Our findings are organized into four overlapping themes: open use of models and simulation results, open validation, open development, and open collaboration. An essential outcome of the discussion is the need for model developers and users to speak with a united voice and promote the role of models in future open science efforts. We introduce a new cross-domain community initiative called Heliophysics Open Modeling Environment (HOME), which will be integrated as an overarching activity within the COSPAR ISWAT Initiative. HOME will serve as a platform for modelers and model users to work together, facilitate community modeling, improve the scientific return on modeling investment, and advance innovation in heliophysics and space weather.

We report the resolution of a halo of X-ray line emission surrounding the zero-age main-sequence G8.5V star HD 61005 by Chandra/ACIS-S. Located only ∼36 pc distant, HD 61005 is young (100 ± 50 Myr) and X-ray bright (∼300 × solar), observed with a nearly edge-on geometry and surrounded by very local interstellar medium (VLISM) material denser than in the Sun’s environs. HD 61005 is known to harbor large amounts of circumstellar dust in a dense ecliptic plane full of millimeter-sized particles plus attached, extended “Wing like structures” full of micron-sized particles, which are evidence for strong VLISM–dust disk interaction. These properties aided our ability to resolve the system’s ∼220 au wide astrosphere, the first ever observed for a main-sequence G star. The observed X-ray emission morphology is roughly spherical, as expected for an astrospheric structure dominated by the host star. The Chandra spectrum of HD 61005 is a combination of a hard stellar coronal emission ( T ∼ 8 MK) at L _X ∼ 6 × 10 ²⁹ erg s ⁻¹ , plus an extended halo contribution at L _X ∼ 1 × 10 ²⁹ erg s ⁻¹ dominated by charge exchange (CX) lines, such as those of O VIII and Ne IX . The Chandra CX X-ray morphology does not track the planar dust morphology but does extend out roughly to ∼110 au where the base of the dust wings begins. We present a toy model of the astrosphere emission produced by stellar wind–VLISM CX interactions, similar to the state of the young Sun when it was only ∼10 ⁸ yr old and transiting through an ∼10 ³ times denser part of the interstellar medium (such as a giant molecular cloud).

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.

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.

Magnetohydrodynamic (MHD) simulations are a useful tool for understanding the propagation of coronal mass ejections (CMEs) in the inner heliosphere and their interaction with the background solar wind. This understanding is important for improving our ability to predict CME properties at Earth. A common approach in models of the inner heliosphere starting from ≈0.1 astronomical unit (au) is to inject CMEs with analytically prescribed magnetic structures—such as magnetic spheromaks—by superimposing the CME’s magnetic field onto the heliospheric magnetic field. However, the superposition method leads to the heliospheric magnetic field penetrating the CME, immediately distorting the CME’s magnetic structure during the injection. In this work, we introduce a new, more physically accurate displacement method for the CME injection into the inner heliosphere by dynamically bending the heliospheric magnetic field around the incoming CME. Using the GAMERA-Helio MHD model of the inner heliosphere (0.1–1 au) and a Gibson–Low model of a CME with an internal magnetic field, we demonstrate that the displacement method preserves the CME’s internal structure, unlike superposition. Moreover, the displacement method produces a current distribution around the CME that is consistent with results from previous coronal MHD simulations with a self-consistent description of CME initiation and evolution. The displacement approach represents a step forward in modeling magnetized CMEs in the inner heliosphere to study their evolution and impacts at Earth.

We analyze ∼40–200 keV energetic particle observations from the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on board the New Horizons (NH) spacecraft from 2007 to 2024 and compare them with similar measurements from the Low Energy Charged Particle experiments on the Voyager 1 and Voyager 2 spacecraft when they were at comparable heliocentric distances (5–60 au). In both Voyager data sets, particle intensities generally decrease with increasing radial distance from the Sun, reaching a minimum in the outer heliosphere before rising again prior to their respective encounters with the heliospheric termination shock (TS). This radial behavior in the intensity-time profiles is described as a heliospheric valley. The NH/PEPSSI time series from 5 au (2007) to 60 au (2024) exhibits a similar decrease in particle fluxes with distance. Analysis of the radial dependence of energetic particle intensities from all three spacecraft normalized by observations at 1 au to account for the solar cycle effects reveals an approximate piece-wise composite power-law relationship, with a slope break (steeper decline) beyond ∼33 au. This break may reflect differences in the dominant transport and acceleration mechanisms operating in the two regions demarcated by this radial break. In addition, a radial scaling method is applied to Voyager observations to best match the NH data. This comparison provides an estimate for the NH TS crossing between 2027 (68 au) and 2034 (83 au).

We explore the capabilities of time-dependent (TD) magnetohydrodynamic (MHD) solar wind simulations with the coupled Wang–Sheeley–Arge (WSA) model of the solar corona and the Grid Agnostic MHD for Extended Research Applications model of the inner heliosphere. We compare TD with steady-state (SS) simulations and in situ observations from multiple spacecraft (Earth, STEREO-A, Parker Solar Probe). We show that TD predictions, although better than SS predictions, substantially mispredict the solar wind at different heliospheric locations. We identified three reasons for that: (1) the uncalibrated WSA velocity formula used to generate solar wind velocities at the inner boundary of a heliospheric domain, (2) the extraction of the WSA boundary conditions for input into MHD models very high in the corona, and (3) the abrupt and partial emergence of active regions from the solar east limb. Evaluation of 1 year of TD predictions at the Earth and STEREO-A locations shows that tuning accordingly the WSA relationship when used with MHD models and extracting the WSA boundary conditions lower in the corona (at 5 R _s instead of 21.5 R _s ) can lead to improved predictions. However, the abrupt emergence of active regions from the east limb of the Sun, which can highly disrupt the magnetic field topology in the corona, is a difficult task to deal with since complete knowledge of the conditions on the solar far side is not currently available. Solar Orbiter Polarimetric and Helioseismic Imager data can help mitigate this effect; however, unless we get a 4 π view of the Sun, we will be unable to completely address it.

We explore the capabilities of time-dependent (TD) magnetohydrodynamics (MHD) solar wind simulations with the coupled WSA model of the solar corona and GAMERA model of the inner heliosphere. We compare TD with steady state (SS) simulations and with in situ data from multiple spacecraft (Earth, STEREO-A, PSP). We show that TD predictions, although better than SS predictions, substantially mispredict the solar wind at different heliospheric locations. We identified three reasons for that: (1) the uncalibrated WSA velocity formula used to generate solar wind velocities at the inner boundary of a heliospheric domain, (2) the extraction of the WSA boundary conditions for input into MHD models very high in the corona, and (3) the abrupt and partial emergence of active regions from the solar east limb. Evaluation of one year of TD predictions at Earth and STEREO-A locations shows that by tuning accordingly the WSA relationship when used with MHD models, and by extracting the WSA boundary conditions lower in the corona (at 5 Rs instead of 21.5 Rs), can lead to improved predictions. However, the abrupt emergence of active regions from the east limb of the Sun which can highly disrupt the magnetic field topology in the corona, is a difficult task to deal with since complete knowledge of the conditions on the solar far side is not currently available. Solar Orbiter Polarimetric and Helioseismic Imager (PHI) data can help mitigate this effect, however, unless we get a 4pi view of the Sun we will be unable to completely address it.