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.

Understanding the connection between magnetospheric dynamics and the aurora has remained one of the most challenging problems in Heliophysics for the last fifty years. One of the more exciting developments in the last two decades was the discovery that Alfvén waves play a significant role, comparable to static electric fields, in accelerating magnetospheric electrons to energies capable of generating auroral arcs during periods of high auroral activity. This discovery has revealed a direct connection between the universal process of magnetic reconnection and the generation of the aurora, but understanding this connection poses some significant challenges for global magnetosphere models. Presently, there does not exist a magnetosphere model capable of simulating the coupling of magnetic reconnection to Earth’s ionosphere on a global scale. The MARBLE project will fill this significant gap by developing a new “collisionless Hall MHD” model capable of following plasma particles and waves from their birth at reconnection sites deep in the magnetosphere all the way to the auroral zone in Earth’s ionosphere. To achieve this goal, MARBLE will be designed from the ground up to make optimal use of the most advanced computer hardware, including large clusters of Graphics Processing Units (GPUs). MARBLE will also embrace Open Science principles at every stage of its development. In addition to being released to the community under an open source license, MARBLE will establish a community driven development approach with transparency, inclusivity, collaboration, and reproducibility as core values. A key goal of the project, consistent with NASA’s Open Science initiative, is to make it possible for non-experts in computational plasma physics to play a meaningful role in the development and validation of the most advanced global magnetosphere models.

Heliophysics is the field that "studies the nature of the Sun, and how it influences the very nature of space - and, in turn, the atmospheres of planetary bodies and the technology that exists there." However, NASA's Heliophysics Division tends to limit study of planetary magnetospheres and atmospheres to only those of Earth. This leaves exploration and understanding of space plasma physics at other worlds to the purview of the Planetary Science and Astrophysics Divisions. This is detrimental to the study of space plasma physics in general since, although some cross-divisional funding opportunities do exist, vital elements of space plasma physics can be best addressed by extending the expertise of Heliophysics scientists to other stellar and planetary magnetospheres. However, the diverse worlds within the solar system provide crucial environmental conditions that are not replicated at Earth but can provide deep insight into fundamental space plasma physics processes. Studying planetary systems with Heliophysics objectives, comprehensive instrumentation, and new grant opportunities for analysis and modeling would enable a novel understanding of fundamental and universal processes of space plasma physics. As such, the Heliophysics community should be prepared to consider, prioritize, and fund dedicated Heliophysics efforts to planetary targets to specifically study space physics and aeronomy objectives.

Key Points:• First-principles, self-consistent geospace modeling will require at least exascale-level computing capabilities; however, the technical skills necessary to develop such simulation codes are not taught as part of Heliophysics training/PhD programs.• Developing exascale Heliophysics codes will require transdisciplinary collaborations between physicists, computer scientists, software engineers, data scientists, and applied mathematics.Such teams must be persistent and formed around specific skills, not specific problems.• We must have stable, positive long-term career outcomes for Heliophysics scientific developers in order to retain knowledge of and promote future innovation in scientific algorithm development and advanced computing techniques.One such way to do this is by funding long-term scientific programming groups, akin to Heliophysics DRIVE Centers.• We must have a balance between promoting innovation via funding short-term closed-source development and allowing the open-source community to benefit from and build on the newest scientific modeling techniques.

Key Points• Geospace, spanning the magnetosphere to mesosphere, is a system of systems in which cross-scale coupling mechanisms play a key role in binding the constituent geospace domains together.Understanding the global geospace consequences of intermediate, or mesoscale, processes is key to understanding fundamental modes of geospace behavior like storms and substorms.

Continue towards a truly open science approach in Heliophysics2. Find new solutions to provide more stability to soft money scientists 3. Work towards more accessibility and equity across different sections of our community 4. Government institutions like NASA and NSF support and provide transinstitutional Human Resource (HR

The field of space physics has a long history of utilizing dimensionality reduction methods to distill data, including but not limited to spherical harmonics, the Fourier Transform, and the wavelet transform. Here, we present a technique for performing dimensionality reduction on ion counts distributions from the Multiscale Mission/Fast Plasma Investigation (MMS/FPI) instrument using a data-adaptive method powered by neural networks. This has applications to both feeding low-dimensional parameterizations of the counts distributions into other machine learning algorithms, and the problem of data compression to reduce transmission volume for space missions. The algorithm presented here is lossy, and in this work, we present the technique of validating the reconstruction performance with calculated plasma moments under the argument that preserving the moments also preserves fluid-level physics, and in turn a degree of scientific validity. The method presented here is an improvement over other lossy compressions in loss-tolerant scenarios like the Multiscale Mission/Fast Plasma Investigation Fast Survey or in non-research space weather applications.

The decadal survey will help guide the Heliophysics community to create opportunities for future success.A uniquely fundamental question will drive science innovations and discoveries in the coming decades: What research environment and community will we build?The most innovative scientific ideas and discoveries develop in safe, inclusive, diverse, accessible, and collaborative environments.These environments strengthen all types of collaborations and advance innovations in concepts and applications.If we ignore this critical aspect of science, current issues regarding diversity, retention, and succession will persist.This paper discusses current critical problems and introduces actionable steps that can cultivate a culture of inclusivity. High Level Recommendations:1. Provide funding and opportunities for professional development focused on awareness of how to improve our culture (e.g., bystander training).2. NASA, NOAA, NSF, universities and other institutions should work closely with research fields in diversity, equity, inclusion, accessibility, and justice (DEIAJ) research to form best practices -then apply those best practices.3. Provide clear accountability, and resources for offenders to learn and grow.4. Track metrics safely and securely to target areas of bias and inequality.5.

The magnitude and complexity of the problems confronting Solar and SpacePhysics from 2024-2033 require the integration of many individuals, groups, data sources, and technologies (i.e., the interconnection of all of our knowledge)2. The solution is a 'knowledge commons': a combination of intelligent information representation and the openness, governance, and trust required to create a participatory ecosystem whereby the whole community maintains and evolves this shared information space 3. To build and sustain a flourishing knowledge commons requires broader participation (e.g., bringing Heliophysicists together with data scientists), adoption of open science practices, and centering responsible and ethical considerations for how we do our research

Over the last decade, Heliophysics researchers have increasingly adopted a variety of machine learning methods such as artificial neural networks, decision trees, and clustering algorithms into their workflow. Adoption of these advanced data science methods had quickly outpaced institutional response, but many professional organizations such as the European Commission, the National Aeronautics and Space Administration (NASA), and the American Geophysical Union have now issued (or will soon issue) standards for artificial intelligence and machine learning that will impact scientific research. These standards add further (necessary) burdens on the individual researcher who must now prepare the public release of data and code in addition to traditional paper writing. Support for these is not reflected in the current state of institutional support, community practices, or governance systems. We examine here some of these principles and how our institutions and community can promote their successful adoption within the Heliophysics discipline.

Magnetohydrodynamics Benchmark from a 2D Riemann Problem based on Case 3 (from Liska et al. Comparison of several difference schemes on 1d and 2d test problems 207 for the euler equations). Since this is technically a hydrodynamic benchmark, its plasma state vectors are inflated by adding the magnetic variables B and setting them to zero.

We use a newly developed global Hall magnetohydrodynamic (MHD) code to investigate how reconnection drives magnetotail asymmetries in small, ion-scale magnetospheres. Here, we consider a magnetosphere with a similar aspect ratio to Earth but with the ion inertial length (δi) artificially inflated by a factor of 70: δi is set to the length of the planetary radius. This results in a magnetotail width on the order of 30 δi, slightly smaller than Mercury's tail and much smaller than Earth's with respect to δi. At this small size, we find that the Hall effect has significant impact on the global flow pattern, changing from a symmetric, Dungey-like convection under resistive MHD to an asymmetric pattern similar to that found in previous Hall MHD simulations of Ganymede's subsonic magnetosphere as well as other simulations of Mercury's using multi-fluid or embedded kinetic physics. We demonstrate that the Hall effect is sufficient to induce a dawnward asymmetry in observed dipolarization front locations and find quasi-periodic global-scale dipolarizations under steady, southward solar wind conditions. On average, we find a thinner current sheet dawnward; however, the measured thickness oscillates with the dipolarization cycle. During the flux-pileup stage, the dawnward current sheet can be thicker than the duskward sheet. This could be an explanation for recent observations that suggest Mercury's current sheet is actually thicker on the duskside: a sampling bias due to a longer lasting “thick” state in the sheet.

The interagency Space Science and Technology Partnership Forum was established in 2015 to identify synergistic efforts and technologies across the U.S. government. While the various space agencies of the U.S. government have distinctly different visions for future operational space systems, all share important foundational common needs. These needs, combined with the maturation of autonomous technology and the prospect of leveraging autonomous systems to address those needs, have led each agency to consider how and when to implement increasing levels of autonomy in their space systems, and how to determine the trustworthiness of an autonomous system. The Partnership facilitated dialogue among the partners, collected and analyzed data on current and desired future levels of capability, and identified gaps to motivate three recommendations that can be addressed within the Partnership community. These recommendations address the need for more robust documenting and socializing of anomalies in space system operations; the need to expand communication and trust within the community of developers, operators, and end users; and the need for a safe development and testing environment for maturing and demonstrating future autonomous space systems. These recommendations will facilitate both near-term programmatic actions and long-term steps for implementing enduring progress towards enabling space trusted autonomy.

We explore the use of Physics-Informed Neural Networks (PINNs) for reconstructing full magnetohydrodynamic solutions from partial samples, mimicking the recreation of space-time environments around spacecraft observations. We use one-dimensional magneto- and hydrodynamic benchmarks, namely the Sod, Ryu-Jones, and Brio-Wu shock tubes, to obtain the plasma state variables along linear trajectories in space-time. These simulated spacecraft measurements are used as constraining boundary data for a PINN which incorporates the full set of one-dimensional (magneto) hydrodynamics equations in its loss function. We find that the PINN is able to reconstruct the full 1D solution of these shock tubes even in the presence of Gaussian noise. However, our chosen PINN transformer architecture does not appear to scale well to higher dimensions. Nonetheless, PINNs in general could turn out to be a promising mechanism for reconstructing simple magnetic structures and dynamics from satellite observations in geospace.

AbstractOn 27 June 1996, the NASA Galileo spacecraft made humanity's first flyby of Jupiter's largest moon, Ganymede, discovering that it is the only moon known to possess an internally generated magnetic field. Resurrecting the original Galileo Plasma Subsystem (PLS) data analysis software, we processed the raw PLS data from G01 and for the first time present the properties of plasmas encountered. Entry into the magnetosphere of Ganymede occurred near the confluence of the magnetopause and plasma sheet. Reconnection‐driven plasma flows were observed (consistent with an Earth‐like Dungey cycle), which may be a result of reconnection in the plasma sheet, magnetopause, or might be Ganymede's equivalent of a Low‐Latitude Boundary Layer. Dropouts in plasma density combined with velocity perturbations afterward suggest that Galileo briefly crossed the cusps into closed magnetic field lines. Galileo then crossed the cusps, where field‐aligned precipitating ions were observed flowing down into the surface, at a location consistent with observations by the Hubble Space Telescope. The density of plasma outflowing from Ganymede jumped an order of magnitude around closest approach over the north polar cap. The abrupt increase may be a result of crossing the cusp or may represent an altitude‐dependent boundary such as an ionopause. More diffuse, warmer field‐aligned outflows were observed in the lobes. Fluxes of particles near the moon on the nightside were significantly lower than on the dayside, possibly resulting from a diurnal cycle of the ionosphere and/or neutral atmosphere.

We study the effects of the Hall electric field on magnetic island coalescence in the large island limit and find evidence for both an elongated electron current sheet layer with a Sweet-Parker-like reconnection rate and a collapsed, Petschek-like electron sheet with a peak reconnection rate approaching the 0.1v(A)B(0) Hall MHD rate. The state observed in our simulations appears to depend on the grid scale. Furthermore, even at the largest system sizes, we find that flux-pileup effects cause the islands to "bounce" despite the presence of a collapsed current sheet allowing fast instantaneous reconnection. The average reconnection rate in the large island limit is slow though the peak reconnection rate is fast.