We report the first observations of continuum emission at the poleward boundary of the dayside auroral oval. Spectral measurements of high-latitude continuum emissions resemble those of Strong Thermal Emission Velocity Enhancement (STEVE), with light characterized by colours such as white, pale pink, or mauve. The emission enhancement spans the entire visible wavelength range. However, unlike STEVE, the high-latitude dayside continuum emission events tightly follow the auroral particle precipitation, often forming field-aligned rays and other dynamic shapes. Some dayside emissions appeared as wide arcs or cloud-like structures within the red-emission-dominated dayside aurora. Our spectral measurements further suggest that the broadband continuum emission may extend into the near-infrared (NIR) regime. Similar to the STEVE emission, low-Earth-orbit measurements of plasma flow in the region of continuum emission show a strong horizontal cross-track velocity shear. Ground-based radar and optical observations provide evidence of both plasma and neutral heating, as well as upwelling, in connection to the continuum emissions. We conclude that the interplay between different heating mechanisms may be an important factor in generating high-latitude continuum emissions.

The 10 May 2024 geomagnetic storm, referred to as the Gannon Storm in this paper, was one of the most extreme to have occurred in over 20 years. In the era of smartphones and social media, millions of people from all around the world were alerted to the possibility of exceptional auroral displays. Hence, many people not only witnessed but also photographed the aurora during this event. These citizen science observations, although not from scientific instruments operated by observatories or research groups, can prove to be invaluable in obtaining data to characterise this extraordinary event. In particular, many observers saw and photographed the aurora at mid-latitudes, where ground-based instruments targeting auroral studies are sparse or absent. Moreover, the proximity of the event to the Northern Hemisphere summer solstice meant that many optical instruments were not in operation due to the lack of suitably dark conditions. We created an online survey and circulated it within networks of aurora photographers to collect observations of the aurora and of disruptions in technological systems that were experienced during this superstorm. We obtained 696 citizen science reports from over 30 countries, containing information such as the time and location of aurora sightings and the observed colours and auroral forms, as well as geolocalisation, network, and power disruptions noticed during the geomagnetic storm. We supplemented the obtained dataset with 186 auroral observations logged in the Skywarden catalogue (https://taivaanvahti.fi, last access: 19 December 2024) by citizen scientists. The main findings enabled by the data collected through these reports are that the aurora was widely seen from locations at geomagnetic latitudes ranging between 30 and 60 degrees, with a few reports from even lower latitudes. This was significantly further equatorward than predicted by auroral oval models. The reported auroral emission colours, predominantly red and pink and intense enough to reach naked-eye visibility, suggest that the auroral electron precipitation contained large fluxes of low-energy (< 1 keV) particles. This study also reveals the limitations of citizen science data collection via a rudimentary online form. We discuss possible solutions to enable more detailed and quantitative studies of extreme geomagnetic events with citizen science in the future.

Abstract. The 10 May 2024 geomagnetic storm was one of the most extreme to have occurred in over 20 years. In the era of smartphones and social media, millions of people from all around the world were alerted to the possibility of exceptional auroral displays. Hence, many people not only witnessed but also photographed the aurora during this event. These observations, although not from traditional scientific instruments, can prove invaluable in obtaining data to characterise this extraordinary event. In particular, many observers saw and photographed the aurora at mid-latitudes, where ground-based instruments targeting auroral studies are sparse or absent. Moreover, the proximity of the event to the northern hemisphere summer solstice meant that many optical instruments were not in operation due to the lack of suitably dark conditions. We created an online survey and circulated it within networks of aurora photographers to collect observations of the aurora and disruptions in technological systems that were experienced during this superstorm. We obtained 696 citizen science reports from over 30 countries, containing information such as the time and location of aurora sightings, observed colours and auroral forms, as well as geolocalisation, network, and power disruptions noticed during the geomagnetic storm. We supplemented the obtained dataset with 186 auroral observations logged in the Skywarden catalogue (https://taivaanvahti.fi) by citizen scientists. The main findings enabled by the data collected through these reports are that the aurora was widely seen from locations at geomagnetic latitudes ranging between 30° and 60°, with a few reports from even lower latitudes. This was significantly further equatorward than predicted by auroral oval models, and that the auroral electron precipitation contained large fluxes of low-energy (< 1 keV) particles. This may explain the predominantly red and pink colours of the aurora as reported by citizen scientists, intense enough to reach naked-eye visibility. This study also reveals the limitations of citizen science data collection via a rudimentary online form. We discuss possible solutions to enable more detailed and quantitative studies of extreme geomagnetic events with citizen science in the future.

Understanding and predicting the structure and evolution of coronal mass ejections (CMEs) in the heliosphere remains one of the most sought-after goals in heliophysics and space weather research. A powerful tool for improving current knowledge and capabilities consists of multispacecraft observations of the same event, which take place when two or more spacecraft fortuitously find themselves in the path of a single CME. Multiprobe events can not only supply useful data to evaluate the large-scale of CMEs from 1D in situ trajectories, but also provide additional constraints and validation opportunities for CME propagation models. In this work, we analyse and simulate the coronal and heliospheric evolution of a slow, streamer-blowout CME that erupted on 2021 September 23 and was encountered in situ by four spacecraft approximately equally distributed in heliocentric distance between 0.4 and 1 au. We employ the Open Solar Physics Rapid Ensemble Information modelling suite in ensemble mode to predict the CME arrival and structure in a hindcast fashion and to compute the 'best-fitting' solutions at the different spacecraft individually and together. We find that the spread in the predicted quantities increases with heliocentric distance, suggesting that there may be a maximum (angular and radial) separation between an inner and an outer probe beyond which estimates of the in situ magnetic field orientation (parametrized by flux rope model geometry) increasingly diverge. We discuss the importance of these exceptional observations and the results of our investigation in the context of advancing our understanding of CME structure and evolution as well as improving space weather forecasts.

The sub-auroral region is located immediately equatorward from the auroral oval, where important magnetosphere-ionosphere-thermosphere dynamical processes take place.Historically, low-Earth orbit satellites as well as ground-based imagers and radars have provided important information about the region.However, in recent years it has become increasingly clear that there are several unexplored aspects of the region that remain elusive in part due to instrumental and observational limitations.Furthermore, the most commonly used large-scale "state of the art" models and theoretical frameworks of the region rely on a quasi steady-state approach which does not accurately represent the rich sub-auroral electrodynamics underway.Recent ground-based and in-situ measurements have revealed new and compelling dynamics underway in the sub-auroral region and reinvigorated the community's interest there.Optical signatures with unusual spectrographic properties, such as SAR arcs, STEVE, and the picket fence, have been associated with extreme and unusual sub-auroral plasma conditions, such as large ion flow velocities (~5-10 km/s) and extreme electron temperatures (>6000 K).Additionally, recent observations have revealed that the transformation of the sub-auroral region into these extreme conditions occurs within minutes.These new measurements pose a significant challenge to our existing theories and available instrumentation, and demonstrate the necessity of new development and deployment of in-situ and remote measurements of the sub-auroral ionosphere.This white paper highlights some of the open questions in the sub-auroral region that have arisen since the previous decadal survey.It provides recommendations on how science advances can be achieved to help close these open questions, and how new discoveries can be made possible.In short: 1.Establishing new and long-term support for unifying citizen and "traditional" scientists is required to sustain observations and discovery in sub-auroral science.2.NASA's Geospace Dynamics Constellation (GDC) mission is required to address and close many outstanding sub-auroral science questions and should be carried-out without delay. 3.New and long-term support for ground-based observations infrastructure is needed to better understand the nature and dynamics of the sub-auroral ionosphere.Existing infrastructure is too sparse in geographic distribution in the sub-auroral region within the United States. 4.In situ measurements of the lower-thermosphere in the sub-auroral region by rockets, lowaltitude satellites, and/or some other techniques are required to conclusively identify the source, energetic pathways, and mechanism of the extreme conditions reported at sub-auroral latitudes.

The current operational dimension available for space weather analysis and operations is not suitable for deep space exploration.As NASA plans for missions beyond the Low Earth Orbit (LEO), new advancements in modeling, observations, and communications are needed to establish a suitable monitoring and protection environment for the missions and the crew.The initial step is to establish multiple observational points that will improve the current analysis/modeling capabilities and extend them to deep space exploration missions.We summarize the value of multiple observational points, outline the current gaps (with examples) in providing operational space weather support for deep space exploration, and propose ideas for missions and international collaborations that will address these existing gaps.These proposed missions and collaborations will be essential to ensure a successful future for deep space exploration.

Resolving 3D physics occurring on multiple spatial and temporal scales is difficult with spacecraft and computer simulations alone, but can be studied much more easily with laboratory plasma experiments.This white paper proposes increasing funding for both human and physical infrastructure development in laboratory plasma facilities, as well as educating early career scientists on how to better utilize laboratory experiments in their own research.

Coronal mass ejections (CMEs) are large eruptions from the Sun that propagate through the heliosphere after launch. Observational studies of these transient phenomena are usually based on 2D images of the Sun, corona, and heliosphere (remote-sensing data), as well as magnetic field, plasma, and particle samples along a 1D spacecraft trajectory (in-situ data). Given the large scales involved and the 3D nature of CMEs, such measurements are generally insufficient to build a comprehensive picture, especially in terms of local variations and overall geometry of the whole structure. This White Paper aims to address this issue by identifying the data sets and observational priorities that are needed to effectively advance our current understanding of the structure and evolution of CMEs, in both the remote-sensing and in-situ regimes. It also provides an outlook of possible missions and instruments that may yield significant improvements into the subject.

The amateur radio community is a global, highly engaged, and technical community with an intense interest in space weather, its underlying physics, and how it impacts radio communications. The large-scale observational capabilities of distributed instrumentation fielded by amateur radio operators and radio science enthusiasts offers a tremendous opportunity to advance the fields of heliophysics, radio science, and space weather. Well-established amateur radio networks like the RBN, WSPRNet, and PSKReporter already provide rich, ever-growing, long-term data of bottomside ionospheric observations. Up-and-coming purpose-built citizen science networks, and their associated novel instruments, offer opportunities for citizen scientists, professional researchers, and industry to field networks for specific science questions and operational needs. Here, we discuss the scientific and technical capabilities of the global amateur radio community, review methods of collaboration between the amateur radio and professional scientific community, and review recent peer-reviewed studies that have made use of amateur radio data and methods. Finally, we present recommendations submitted to the U.S. National Academy of Science Decadal Survey for Solar and Space Physics (Heliophysics) 2024–2033 for using amateur radio to further advance heliophysics and for fostering deeper collaborations between the professional science and amateur radio communities. Technical recommendations include increasing support for distributed instrumentation fielded by amateur radio operators and citizen scientists, developing novel transmissions of RF signals that can be used in citizen science experiments, developing new amateur radio modes that simultaneously allow for communications and ionospheric sounding, and formally incorporating the amateur radio community and its observational assets into the Space Weather R2O2R framework. Collaborative recommendations include allocating resources for amateur radio citizen science research projects and activities, developing amateur radio research and educational activities in collaboration with leading organizations within the amateur radio community, facilitating communication and collegiality between professional researchers and amateurs, ensuring that proposed projects are of a mutual benefit to both the professional research and amateur radio communities, and working towards diverse, equitable, and inclusive communities.

In the past decade, citizen science has emerged as a catalyst for scientific discovery in heliophysics.While perhaps initially perceived by some as a novel way of crowd-sourcing data collection and/or analysis tasks that doubled as a public relations exercise, it is now clear that citizen science has established itself as a mainstream method of conducting heliophysics research.Here, we put forward that citizen science has matured to the point where it will foster discovery in heliophysics in the coming decade and beyond.Funding and programmatic efforts should be significantly enhanced and directed to harness the potential of citizen science activities.This must be done with generative partnerships in a way that promotes equity and respect between the citizen and traditional science communities.

The amateur radio community is a global, highly engaged, and technical community with an intense interest in space weather, its underlying physics, and how it impacts radio communications. Over the past century, the amateur radio community has made significant contributions to ionospheric, space, and atmospheric science and it continues to innovate and contribute today. This community is ideally suited to collaborate with professional heliophysics researchers. In this white paper, we make recommendations to foster and further develop this relationship for community benefit. Our recommendations are based on experience with the Ham Radio Science Citizen Investigation organization (HamSCI, hamsci.org), a citizen science project established in 2015 for this purpose. We recommend allocating resources for amateur radio citizen science research projects and activities, developing amateur radio research and educational activities

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

Whitepaper #255 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research; infrastructure/workforce/other programmatic. Additional topics: ground-based missions/projects; emerging opportunities; state of the profession; […]

Citizen science connects scientists with the public to enable discovery, engaging broad audiences across the world. There are many attributes that make citizen science an asset to the field of heliophysics, including agile collaboration. Agility is the extent to which a person, group of people, technology, or project can work efficiently, pivot, and adapt to adversity. Citizen scientists are agile; they are adaptable and responsive. Citizen science projects and their underlying technology platforms are also agile in the software development sense, by utilizing beta testing and short timeframes to pivot in response to community needs. As they capture scientifically valuable data, citizen scientists can bring expertise from other fields to scientific teams. The impact of citizen science projects and communities means citizen scientists are a bridge between scientists and the public, facilitating the exchange of information. These attributes of citizen scientists form the framework of agile collaboration. In this paper, we contextualize agile collaboration primarily for aurora chasers, a group of citizen scientists actively engaged in projects and independent data gathering. Nevertheless, these insights scale across other domains and projects. Citizen science is an emerging yet proven way of enhancing the current research landscape. To tackle the next-generation’s biggest research problems, agile collaboration with citizen scientists will become necessary.

Context: Coronal mass ejections (CMEs) are eruptions of plasma from the Sun that travel through interplanetary space and may encounter Earth. CMEs often enclose a magnetic flux rope (MFR), the orientation of which largely determines the CME's geoeffectiveness. Current operational CME models do not model MFRs, but a number of research ones do, including the Open Solar Physics Rapid Ensemble Information (OSPREI) model. Aims: We report the sensitivity of OSPREI to a range of user-selected photospheric and coronal conditions. Methods: We model four separate CMEs observed in situ by Parker Solar Probe (PSP). We vary the input photospheric conditions using four input magnetograms (HMI Synchronic, HMI Synoptic, GONG Synoptic Zero-Point Corrected, and GONG ADAPT). To vary the coronal field reconstruction, we employ the Potential-Field Source-Surface (PFSS) model and we vary its source-surface height in the range 1.5--3.0 R$_{\odot}$ with 0.1 R$_{\odot}$ increments. Results: We find that both the input magnetogram and PFSS source surface often affect the evolution of the CME as it propagates through the Sun's corona into interplanetary space, and therefore the accuracy of the MFR prediction compared to in-situ data at PSP. There is no obvious best combination of input magnetogram and PFSS source surface height. Conclusions: The OSPREI model is moderately sensitive to the input photospheric and coronal conditions. Based on where the source region of the CME is located on the Sun, there may be best practices when selecting an input magnetogram to use.

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 large-scale observational capabilities of distributed instrumentation fielded by amateur radio operators and radio science enthusiasts offers tremendous opportunity for advancement in the fields of heliophysics, radio science, and space weather forecasting and operations. Well-established amateur radio networks such as the RBN, WSPRNet, and PSKReporter already provide a rich, ever-growing long-term dataset of bottomside ionospheric observations. Conversely, up-and-coming purpose-built citizen science networks, and the associated novel instruments, offer opportunities for citizen scientists, professional researchers, and industry to field instrument networks optimized to make measurements targeting specific science questions and operational needs. When these measurements are used in conjunction with existing networks of professional instrumentation,

We analyzed spectropolarimetric data from the Swedish 1 m Solar Telescope to investigate the physical properties of small-scale magnetic cancellations in the quiet Sun photosphere. Specifically, we looked at the full Stokes polarization profiles along the Fe i 557.6 nm and of the Fe i 630.1 nm lines measured by the CRisp Imaging SpectroPolarimeter to study the temporal evolution of the line-of-sight magnetic field during 42.5 minutes of quiet Sun evolution. From this magnetogram sequence, we visually identified 38 cancellation events. We then used the Yet Another Feature Tracking Algorithm to characterize the physical properties of these magnetic cancellations. We found on average 1.6 × 10 16 Mx of magnetic flux canceled in each event with an average cancellation rate of 3.8 × 10 14 Mx s −1 . The derived canceled flux is associated with strong downflows, with an average speed of V LOS ≈ 1.1 km s −1 . Our results show that the average lifetime of each event is 9.2 minutes with an average of 44.8% of initial magnetic flux being canceled. Our estimates of magnetic fluxes provide a lower limit since studied magnetic cancellation events have magnetic field values that are very close to the instrument noise level. We observed no horizontal magnetic fields at the cancellation sites and therefore cannot conclude whether the events are associated with structures that could cause magnetic reconnection.