Department of Space

Rapid urbanisation in Oman’s extreme climate is intensifying water stress and expanding Urban Heat Islands (UHI), which directly threaten population health, economic productivity, and municipal budgets. Urban planners must optimise resource allocation and capital investments while maintaining urban livability. This study presents a Digital Twin (DT) framework, grounded in the Astra Terra architecture, to model the dual benefits of Nature-based Solutions (NbS) for UHI mitigation and hydrological resilience. In contrast to traditional models that focus exclusively on vegetation, this approach incorporates "wetness" as a primary variable in regulating the urban microclimate.The methodology integrates a federated data ecosystem, utilising the Copernicus Climate Data Store (CDS) for baseline indicators and Landsat 8 thermal imagery for hotspot identification. A Data Fusion Core merges satellite Earth Observation data with three-dimensional urban morphology. The framework follows FAIR data principles and high-performance computing (HPC) standards, ensuring scalability and policy-driven simulation capabilities compatible with the Destination Earth (DestinE) platform.As a proof-of-concept demonstrator, this framework explores the theoretical ability to simulate urban responses to varying 'wetness' levels. This initial iteration focuses on modeling 'wet infrastructure' to establish the basic principles of hydro-thermal feedback in arid environments. By mapping existing wadis and topographical depressions, the framework simulates Blue-Green Infiltration Basins and water-retention zones. These scenarios are used to evaluate two critical environmental and economic responses:Hydrological Resilience and Financial Optimisation: Zones are modeled as Managed Aquifer Recharge (MAR) sites. The Digital Twin simulates how infiltration rates stabilize local aquifers, thereby reducing the long-term costs associated with water scarcity management. Incorporating native species such as Acacia and Date palm, the model demonstrates ecological balance with minimal maintenance requirements.Thermal Cooling and Public Health: The framework quantifies the thermal response to increased soil moisture. Simulations indicate that higher thermal inertia and latent heat dissipation can reduce surface temperatures by 3–5°C near critical infrastructure. This temperature reduction is directly associated with improved population mobility and reduced heat-related health risks, both of which are essential for sustaining economic activity and resident well-being.Eco-Hydrological Feedback: "Greenness" serves as a biological indicator of subsurface water availability. The Digital Twin models the feedback loop in which urban vegetation protects water resources from evaporation, thereby supporting the longevity of urban investments.Impact and Decision Support: Through advanced analytics, the Digital Twin provides actionable insights to help planners prioritise multifunctional spaces. By demonstrating that interventions are both thermally effective and economically viable, this approach offers a practical roadmap for reducing complexity in urban planning and enhancing the climate resilience of heat-stressed arid cities.

Since April 2023, solar flares have been simultaneously observed by the Spectrometer/Telescope for Imaging X-ray (STIX) onboard ESA’s Solar Orbiter and by the Hard X-ray Imager (HXI) onboard the Chinese ASO-S mission. The two telescopes independently measure 2D Fourier components (visibilities) of the flaring X-ray radiation from different vantage points. However, by combining their datasets, it is possible to obtain a sampling of the 3D Fourier transform of thermal hard X-ray sources in solar flares. This combined dataset allows reconstructing the 3D morphology of the flaring sources by solving an inverse imaging problem.In this presentation, we describe the methodology we developed for 3D reconstruction of thermal hard X-ray sources in solar flares from combined STIX/HXI data. We present the results obtained in the case of the X9.1 GOES class event which occurred on October 3, 2024. During this event, the two instruments were in an ideal configuration, where the separation angle between them and the flaring site was approximately 90 degrees. We validate the 3D reconstruction by comparing them with the 2D images independently reconstructed from STIX and HXI data. Finally, we determine the altitude of the reconstructed X-ray source above the solar surface as a function of time, and we derive estimates of its radial velocity.

On March 15, 2015 a Coronal Mass Ejection (CME) associated with a C9.1 class flare caused the biggest geomagnetic storm of solar cycle 24. We present a numerical modeling study of the pre-eruption energetic phase, onset and evolution of this CME in the solar corona and the inner heliosphere. The CME initiation is modeled using the STITCH (STatisTical Injection of Condensed Helicity) methodology with the extended 3D global magnetohydrodynamic (MHD) model of the solar corona, Alfven Wave Solar atmosphere Model (AWSoM). STITCH is a statistical approximation of the hard to capture (numerically) small scale photospheric motions, by injecting a net helicity and forming sheared filament channels over polarity inversion lines (PILs). This emulates the energy build-up due to the small-scale convective motions and magnetic reconnection on the solar surface. In comparison to analytical flux-rope models, this method provides a realistic way to investigate the onset and eruption of a CME from the solar surface utilizing observations of the photospheric magnetic field. The shearing of the PIL of the erupting active region energizes the filament channel leading to flare reconnection and eruption of the CME flux-rope structure. We describe the magnetic and plasma properties of the pre-eruption and post eruption phase of the CME and its evolution characteristics.

Abundance ratios of heavy ions in the solar wind can be used to probe the low solar corona through the freeze-in and First Ionization Potential (FIP) effects, while their speeds and temperatures can probe both collisionless and collisional processes in the solar wind. We present results demonstrating how heavy ion properties act as diagnostics for phenomena spanning different regimes within the heliosphere. Through a cross-correlation analysis between heavy ion density ratios and proton specific entropy from 1998-2011, we find that the variability in solar wind fluid entropy freezes-in between approximately 1.4-1.8 solar radii in heliocentric distance, constraining time-dependent processes in solar wind formation. Additionally, by incorporating proton temperature anisotropies to compare with heavy ion temperatures, we observe that certain heavy ion species are less subject to the CGL conditions in the highly collisionless solar wind than protons are, placing constraints on inter-species energy partitioning. These analyses, based on measurements of heavy ions at 1 AU, can be extended to data collected by the Heavy Ion Sensor onboard Solar Orbiter. Through the incorporation of proton anisotropies and heavy ion measurements across variable heliocentric distances, these extended analyses will further probe the thermodynamic evolution of the solar wind.

Surface melting and runoff account for about half of the current mass loss of the Greenland Ice Sheet. Regional climate models (RCMs) project runoff to increase further over the 21st century, but the magnitude of this trend varies strongly between different models. This variability arises because RCMs rely on simplified representations of the complex firn hydrological system in Greenland’s percolation zone. However, key parameters for parametrizing meltwater retention and runoff processes remain poorly constrained due to a lack of time-resolved, in situ observations of firn liquid water content.We address this gap by demonstrating that the Autonomous phase-sensitive Radio-Echo Sounder (ApRES) can continuously trace the amount of liquid water in the firn. At three automatic weather station sites on the ice sheet (KAN_U, DYE-2 and Camp Century), we acquired hourly ApRES time series between spring 2023 and 2025, covering two melt seasons. By analyzing these observations in combination with a firn model, we quantify rates of lateral meltwater flow. Comparison with runoff simulations from three RCMs shows that all models overestimate local runoff at KAN_U, and that some even predict runoff at DYE-2 (2124 m a.s.l.), where our observations indicate that all meltwater is refrozen. Expanding these observations will support the development of improved representations of Greenland’s firn hydrological system in RCMs and ultimately enhance the accuracy of GrIS mass balance projections.

We have developed and implemented a new data-driven method to initiate a coronal mass ejection (CME) in the Alfven Wave Solar atmosphere Model (AWSoM). Our new approach uses an HMI vector magnetogram observed prior to the CME eruption. First we obtain an approximate non-linear force free (NLFF) magnetic field in the vicinity of the active region with a magnetofriction code. Next, this magnetic field is inserted into the AWSoM steady state solution in place of the original potential field to obtain an approximate steady state with the full physics of AWSoM. At this point the currents present in the NLFF field are ignored. Finally, we return to using the potential field as the background so that the difference of the NLFF and potential fields becomes the initial magnetic field structure of the CME. Solving in time-accurate mode with the NLFF field currents fully included results in an eruption. We report on the results obtained with this new CME initiation method for several events.

Laser guide stars (LGSs) have been deployed for the last 20-30 years in ground-based astronomical telescopes to overcome the limited sky coverage of classical adaptive optics (AO) systems. Unfortunately, slow altitude drifts of the sodium layer compromise focus measurements, generating the so-called slow focus error, and, consequently, a natural guide star (NGS) is needed to compensate that error. The Keck I telescope AO system uses a 20x20 Shack-Hartmann (SH) wavefront sensor (WFS) for slow focus tracking (with a 5x5 mode used on fainter stars). This approach is far from optimal due to limited sky coverage, since the available NGSs are usually very faint. Our goal is to develop a different technique for slow focus tracking and make it fully operational using focal plane wavefront sensing (FPWFS), which can significantly increase sky coverage and allow slow focus tracking at higher frequencies, reducing the lag error. The Keck I near-infrared (NIR) tip-tilt sensor, known as TRICK, is used to obtain the focal plane images without any hardware modifications being necessary. We develop, characterize, and compare three different FPWFS algorithms, namely Gerchberg-Saxton (GS), linearized focal plane technique (LiFT), and Gaussian fit (Gf). These algorithms are studied for the specific purpose of slow focus sensing in the NIR (H and K bands) using numerical simulations and data collected at Keck in 2025 (bench and on-sky). The three algorithms were studied and characterized against different criteria such as linearity, computational costs, and resistance to low signal-to-noise ratio and/or residuals. From the results obtained, the main candidate for an on-sky deployment was GS, for which the main deciding factor was its higher stability and robustness under the presence of residuals. For that reason, on-sky tests in closed loop were made with GS. On-sky tests showed promising results, with GS successfully compensating for purposely introduced focus errors, even under the presence of high turbulence conditions. These tests represent an important step toward the full operationalization of this tool, expected in the coming months. This work can also be extrapolated to other existing 8-10 m class telescopes, or even future 30-40 m class telescopes, where the use of FPWFS can significantly improve sky coverage and reduce the lag error.

ABSTRACT Close to the Sun, Parker Solar Probe (PSP) traverses the sub-Alfvénic solar wind, a magnetically controlled plasma environment. Farther from the Sun, the magnetic field amplitude and plasma density weaken enough to establish a super-Alfvénic environment where kinetic energy and turbulence become more prominent. Switchbacks (i.e. large directional deviations from the mean field) are shown to occur almost exclusively in the super-Alfvénic regime. In this study, we analyse magnetic fluctuations from PSP encounters 8 through 19 to study their relationship to Alfvén Mach number ($M_\mathrm{ A}$) and switchback parameter (Z). We find that the fluctuation of the magnetic field magnitude normalized to the mean magnetic field and of the radial velocity normalized to local Alfvén speed increase with both Alfvén Mach number and switchback parameter. However, there is distinct saturation in the increments of the normalized radial velocity fluctuations in the Alfvén Mach number range of $\sim$4–6. Results are interpreted in terms of the Chandrasekhar criterion for Kelvin–Helmholtz activity. Overall, these findings are in agreement with earlier studies suggesting switchback generation through non-linear shear flow dynamics.