Integrating plasmasphere, ionosphere and thermosphere observations and models into a standardised open access research environment: The PITHIA-NRF international project

u Institut de Recherche en Astrophysique et Plane ´tologie (IRAP), Universite ´de Toulouse, ROUTE DE NARBONNE 118, TOULOUSE CEDEX 9 31062, France Available online at www.sciencedirect.com ScienceDirect Advances in Space Research 75 (2025) 3082–3114 www.elsevier.com/locate/asr Integrating plasmasphere, ionosphere and thermosphere observations and models into a standardised open access research environment: The PITHIA-NRF international project Anna Belehaki a,⇑ , a Iaasars, National Observatory of Athens (NOA), Metaxa and Vas. Pavlou, Palaia Penteli, 15236, Greece Ingemar Ha ¨ggstro ¨ m b , b Eiscat Scientific Association (EISCAT), Rymdcampus 1, Kiruna 981 92, Sweden Tamas Kiss c , c The University of Westminster LBG (UOW), Regent Street 309, London W1B 2UW, United Kingdom Ivan Galkin d,e , d Borealis Global Designs Eood (BGD), BLVD Maria Louisa 24 Entr A FLOOR 1 AP 1, Varna 9000, Bulgaria e Center for Atmospheric Research, University of Massachusetts Lowell (UML), 600 Suffolk Street, Lowell, MA 01854, USA Anders Tjulin b , Ma ´ria Miha ´likova ´ b , Carl-Fredrik Enell b , Gabriel Pierantoni c,1 , Yin Chen f , f Stichting EGI (EGI), Science Park 140, Amsterdam 1098 XG, the Netherlands Gergely Sipos f , Sean Bruinsma g , g Centre National D’etudes Spatiales (CNES), Space Geodesy Office, 18 Avenue E. Belin, 31401 Toulouse, France Viviane Pierrard h , h RoyaI Belgian Institute for Space Aeronomy (BIRA), AVENUE CIRCULAIRE 3, Bruxelles 1180, Belgium David Altadill i , i Observatorio del Ebro Fundacion, CSIC - Universitat Ramon Lull, Roquetes 43520, OE, Spain Antoni Segarra i , Vı ´ctor Navas-Portella i , Emanuele Pica j , Luca Spogli j , j Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via di Vigna Murata 605, 00143, Rome Lucilla Alfonsi j , Claudio Cesaroni j , Vicenzo Romano j , Sara Mainella j , Pietro Vermicelli k , k SpacEarth Technology (SET), Viale dell’Astrono mia 18, 00144 Rome, Italy Tobias Verhulst l , l Royal Meteorological Institute of Belgium(RMI), AVENUE CIRCULAIRE 3, Bruxelles 1180, Belgium Stefaan Poedts m,n , m Katholieke Universiteit Leuven (Ku Leuven), Dept. of Mathematics/Cm PA, Oude Markt 13, Leuven 3000, Belgium n University of Maria Curie-Skłodowska (UMCS), ul. Marii Curie-Sk łodowskiej 1, 20-031 Lublin, Poland Manuel Herna ´ndez-Pajares o , Dalia Buresova p , p Ustav Fyziky Atmosfery AV CR, v.v.i. (IAP), BOCNI II 1401, PRAHA 4 141 31, Czech Republic Jan Rusz p , Jaroslav Chum p , Fabien Darrouzet h , Edith Botek h , Hanna Rothkaehl q , q Centrum Badan Kosmicznych Polskiej Akademii Nauk (CBK PAN), Bartycka 18A, 00-716 Warsaw, Poland Barbara Matyjasiak q , Mariusz Pozoga q , Marcin Grzesiak q , David Chan You Fee c , Dimitris Kagialis c , Ioanna Tsagouri a , Angeliki Thanasou a , Themistocles Herekakis a , Jean-Marie Chevalier r , r Koninklijke Sterrenwacht van Belgie (ROB), Avenue Circulaire 3, Bruxelles 1180, Belgium Nicolas Bergeot r , Alexandre Winant h , Maaijke Mevius s , s The Netherlands Institute for Radio Astronomy (ASTRON), Oude Hoogeve ensedijk 4, 7991 PD Dwingeloo, The Netherlands Ben Witvliet t , t University of Twente, Faculty of EEMCS, Radio Systems, Enschede, the Netherlands Victoria Graffigna o , o Universitat Politecnica de Catalunya (UPC), Mod. C3 Campus Nord UPC, c/ Jordi Girona 1-3, 08034 Barcelona, Spain Aure ´lie Marchaudon u , David Wenzel v , v Deutsches Zentrum Fuer Luft - und Raumfahrt ev (DLR), Kalkhorstweg 53, 17235 Neustrelitz, Germany Martin Kriegel v , Ju ¨rgen Matzka w , w Helmholtz Zentrum Potsdam Deutsches Geoforschungszentrum GFZ, TELEGRAFENBERG 17, Potsdam 14473, Germany Guram Kervalishvili w , Tero Raita x , Reko Hyno ¨nen x , Jurgen Watermann y ⇑ Corresponding author at: IAASARS, National Observatory of Athens, Palaia Penteli 15236, Greece. E-mail address: [email protected] (A. Belehaki). 1 Deceased, December 2023. https://doi.org/10.1016/j.asr.2024.11.065 0273-1177/©2024 COSPAR. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). w x Oulun Yliopisto (SGO), Pentti Kaiteran Katu 1, Oulu 90014, Finland y Jfwconsult (JFW), LA Tetrade Chemin De Pichot, Tourrettes 83440, France A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Received 15 August 2024; received in revised form 24 November 2024; accepted 26 November 2024 Available online 2 Decembe r 2024 Abstract The PITHIA-NRF project ‘‘Plasmasphere Ionosphere Thermosphere Integrated Research Environment and Access services: a Network of Research Facilities” aims at building a European distributed network that integrates observations from space and ground, data processing tools and models to support scientific research on the Plasmasphere-Ionosphere-Thermosphere system. PITHIA-NRF is designed to provide formalised open access to experimental facilities, data and models, standardised data products, and training services. Participating organisations that operate these facilities, formed twelve nodes in eleven European countries. These nodes work on optimising their observing facilities and offer trans-national access to scientists and engineers. The PITHIA-NRF e-Science Centre is a core element of the project. Its design and evolution are controlled by a systematic ontology which governs the collection of scientific observations and research models, jointly termed data collections, which are registered with the e-Science Centre. Several tens of data collections are being registered. Data collection registrations adhere to FAIR principles and transparent quality measures to a large extent. The e-Science Centre facilitates the execution of research projects proposed by researchers from inside and outside the PITHIA-NRF consortium which require trans-national access to and understanding of data collections (observations and models) residing at one or several PITHIA-NRF nodes. Upon completion of the project a comprehensive collection of observations and models will have been gathered by the e-Science Centre for the benefit of efficient scientific research which relies on Europe-wide collaboration. ©2024 COSPAR. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/). 1. Introduction Physical processes in the Earth’s ionosphere, thermosphere, and plasmasphere result in an extremely complex physical system which is the source of many scientific, operational, societal, and environmental challenges that affect the smooth and uninterrupted operation o f technological systems. Some indicative affected applications are: (1) high-frequency (HF) radio communication and localisation (Knipp, 2016; Witvliet, 2016), geolocation systems and associated groundand satellite-based aug mentation systems (Roy, 2013); (2) space-based communic ations (Dorman, 200 5), communication between the Earth and ground stations and rovers on the Moon, on Mars and other planets (Barbieri, 2004; Bergeot et al., 2019); (3) communication with deep space missions (Woo, 20 07); (4) low-frequency radio astronomy and SyntheticAperture Radar (SAR) observations (Pi, 2015). The importance of the socioeconomic impact of these effects (Vermicelli et al., 2022) indicates the need to release improved nowcasting and forecasting tools for the upper atmosphere and the plasmasphere. To meet this goal, a first fundamental step is to advance access to science data, analysis tools and scientific models and facilitate the transition of models from research to operational status; this is the main objective and the ambition of the Research Infrastructure project PITHIA-NRF, implemented with funding from the European Commission Horizon 2020 Programme. PITHIA-NRF, the Plasmasphere Ionosphere Thermosphere Integrated Research Environment and Access services: a Network of Research Facilities, aims to build a European distributed network integrating observing facilities, data collections, data processing tools and prediction models dedicated to ionosphere, thermosphere and plasmasphere (ITP) research. PITHIA-NRF is designed to provide formalised access to experimental facilities, to Findable, Accessible, Interoperable, Re-usable (FAIR) data, to standardised data products and to training and innovation services. PITHIA-NRF paves the way for the establishment of a research environment that provides ne observing technologies, procedures and tools that support transition of research models to high-level data products tuned to meet the requirements of the technologies concerned, linking best-in-class R&D facilities for the provision of seamless multi-technology services. 3083 European institutions operate a large number of worldclass groundand space-based instruments dedicated to observing the Earth’s ionosphere, thermosphere and plasmasphere. The management and processing of the data collections acquired by these heterogeneous instruments is not standardised and the policies for access and exploitation are different and mainly tuned to national priorities. Due to this fragmented operation, and different access policies, researchers in Europe and worldwide cannot exploit the full potential of these important research assets, despite the significant investments made mainly through national and regional funds. The PITHIA-NRF integration scheme unites the research facilities, databases and models in a single research environment and renders them easily accessible to the European researchers and to all interested individu- a als and organisations, ensuring their optimal use and pro - moting cooperative development. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 The research facilities serve the following fun damental scientific demands: 1. Access to the network facilities by scientists and engineers, for the implementation of user-design projects, using the unique observi ng capabilities that PITHIA-NRF offers. 2. Access to long-term observational data of the nearEarth space environment to build a comprehensive view of the Iono sphere – Thermosphere – Plasmasphere system, and also to develop and validate models. 3. Access to validated models and their results and to relevant training material on the modelling concepts, and on the phy sics principles embedded in the empirical models, addressed to the new generation of researchers. 4. Access to a platform that provides tools for the development and integration of new models for near-Earth space, which are indispensable for describing, explaining and ultimately forecasting the behaviour of this complex system, and mitigating adverse space weather effects on vulnerable technologies. From its inception, PITHIA-NRF has been an integral part of the global network of research infrastructures (Ishii et al., 20 24), as its foundation is based on integration principles set by EGI (a pan-European e-infrastructure), URSI, and ESA (SSA and EO Programmes) regarding data model standards and maturity scales. It relies on data collection and management standards and policies set by the EOSC, mainly provided by URSI, the IGS GNSS network (such as raw GNSS RINEXand global VTEC IONEXformats) and CCMC/NASA. The adoption of specific standards is considered in the PITHIA-NRF data policy definition, which is necessary given the particularities of the upper atmosphere data sets that are a mi xture of ground-based and spaceborne data and contain a variety of data products extracted from models or processed with data curation tools. Fig. 1 shows the structure of PITHIA-NRF. An advanced level of integration is obtained via the alignment and use of common standards, observat ion strategies, data management strategies, data formats, scientific models, and e-infrastructures. The integration is achieve d through: The establishment of the e-Science Centre (eSC) for the registration of data collections, their discovery, access and re-use. Data collections registered in the eSC are available with open access. However, registrations in the eSC are accepted by authorised users eithe r from the project beneficiaries or from any other party, such as TransNational Users or institutions willing to use the eSC as a central repository for data and models. The development of policies for common data man agement and quality control. The creation of a space physics ontology and community metadata standard facilitating the establishment of a shared language, essential for streamlined data integration. The optimisation of the operation of the observing facilities operated within the PITHIA-NRF nodes and the provision of standardised access to scientists and engineers to conduct Research and Development projects. 3084 Models and data made available at the Nodes are made compatible with national e-infrastructures brought together in EGI. The integrated system provides an extended exploitation potential for users regarding observing facilities , data, application models and workflows. Delivery towards users is done via the PITHIA-NRF eScience Centre and is promoted by EOSC. The following sections provide details about the implementation of integrated activities and the outlook for the sustainabil ity of the PITHIA-NRF Research Infrastructure on a long-term perspective. 2. The network of research facilities The Network of Research Facilities consists of 12 nodes that provide access to key observing and data processing infrastructures for the investigation and modelling of physical processes acting in the Earth’s upper atmosphere. 2.1. Research priorities in PITHIA-NRF nodes Table 1 provides a short description of the research specialisation of each node and the indicative research topics for project implementation by external research users. The PITHIA-NRF nodes provide access to the dat collections through its local databases. Within the course of the project the majority of these local databases are upgraded to meet the FAIR requirements and their metadata are registered in the eSC. In this way, the eSC became the central node of the network of local databases and it is the end point from where PITHIA-NRF data collections can be discovered with open access. However, the data itself are hosted and maintained by the nodes . It depends on the policy of each node whether the registered data collections are updated in real-time, or with a latency which is again defined by the policy of the data owners. The eSC, as the main access point for the data collections, provides access also to global data bases of key interest for the PITHIA-NRF community such as the GIRO database for Digisonde data, the IGS database for GNSS data, and the GFZ and DTU databases for geomagnetic and solar indices. The eSC is continuously updated with new registrations and hopefully more data collections will be accessible in the near future to facilitate Research and Innovation projects implemented in the nodes. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Fig. 1. PITHIA-NRF integratio n concept. 2.2. Guided access to PITHIA-NRF nodes via TNA projects Access to PITHIA-NRF nodes is provided to selected users after the successful evaluation of their Transnational access (TNA) research proposals. The access can be granted for projects requiring on-site work and/or remote execution. Once a proposal is positively evaluated and accepted for implementation in a PITHIA-NRF node, the TransNational Access (TNA) project is implemented. The PITHIA-NRF TNA programme has released seven open calls since the start of the PITHIA-NRF Horizon 2020 project. These calls are detailed on the project web site, regarding the commitments from the side of the project and the side of the applicants and the evaluation criteria. In the frame of the PITHIA-NRF TNA programme 47 projects are completed or currently implemented. The choices available to the applic ants are summarised in Fig. 2. The user gets access to observing facilities operated by the node (in case of on-site access) and to local databases and/or to the eSC (for on-site and remote implementation). Depending on the specific TNA project, the first phase usually includes the collection of the require d data either through special campaigns or through the databases and the eSC. The second phase includes the processing of the collected data: If scientific observations are collected for a special campaign, data (acquisitions) can be evaluated regarding the quality (see section 5) and can be registered in the eSC as a new data catalogue. 3085 If the collected data are used for the development of a scientific model, then after the completion of an iterative procedure that includes model design – development – verification – validation, the results of the model (computations) can be registered in the eSC as a new data collection. The PITHIA-NRF ontology (Galkin, 2023) supports the registration of several types of scientific models, including empirical and physics-based models. The model execution and the storage of results depend on the data collection interaction method that will be chosen by the user (see Section 4.2). If the collected data are used for the calibration of an instrument, the results can be published (registered) in the eSC in the form of a catalogue and/or can be transformed to a new high level data product and be used for a new innovation project. High level data products result from intensive data processing applied over a set of data (acquisitions and computations) and very often require a chain of scientific models to be used in the processing chain (workflows). 2.3. Research results obtained from TNA projects The operation of PITHIA-NRF nodes as a network of research facilities provides a framework for exchange of expertise, new ideas and concepts. Through this activity, interfaces are being developed with innovation actions, reaching out to the engineering community, and the space agencies which have specific requirements for technology readiness and standardisation in instrumentation and soft- A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Table 1 Nodes research specialisation. PITHIA-NRF nodes Indicative research topics for implementation by scientific users NOA node: HF VI experiments and ionospheric models Operated by NOA, Athens (Palaia Penteli), Greece Ionospheric modelling for nowcasting and forecasting purposes: Modelling formulation of ionospheric storm effects at middle latitudes driven by solar wind input; Data driven ionospheric specification models, using different training data sets and/or deep-learning techniques; Reconstruction of electron density profile ingesting ground and spacebased observations Validation of ionospheric specification models compatible with international practices Ionospheric data quality control: development of higher-level dataproducts based on ionospher ic autoscaled data filtering algorithms Ionospheric irregularities and travelling ionospheric disturbances (TIDs): identification and propagation patterns for TIDs in the bottomside and topside ionosphere; identification of post-seismic effects in the ionosphere Digisonde experiments: vertical soundings in autonomous and synchronised modes; joint experiments/special campaigns with bistatic HF sounders’ operations. Auroral and polar cap electrodynamics Space environment atmosphere coupling at the statistical southern edges of the polar vortex and the auroral oval Thermosphere-ionosphere coupling Combined ISR and active HF Heating experiments ISR WorldDay collaboration Meteoroids, dust particles and near-Earth objects Ionospheric 3D imaging Dynasonde database (DSND/NeXtYZ parameters, ionospheric irregularities) EISCAT node: Incoherent scatter radar (ISR) and other VHF/UHF high power large aperture radar experiments, HF ionospheric heating experiments, Dynasonde data Operated by EISCAT, Kiruna, Sweden LOFAR node: low-frequency radio observations Operated by ASTRON, The Netherlands Ionospheric scintillation at low radio frequencies: Assessment of any association with scintillation seen by GNSS Assessment of any association with large-scale structures (e.g., TIDs) detected and modelledby other instruments. Quantification of the impact of magnetosphere–ionosphere coupling on auroral region boundary layers behaviour using satellite in situ measurements from DEMETER, RELEC, COSMIC, as well as measurements from ground-based infrastructures Implementation of novel techniques based on LOFAR diagnostics for determining the characteristics of small and middle scales ionospheric irregularities CBK/PAS node: multi-instrument diagnostics of plasma structures Operated by CBK/PAS, Warsaw, Poland SGO node: High latitude ionosphere physics experiments Operated by the Sodankyla Geophysical Observatory, Finland Auroral electrodynamics using entire Finnish Pulsation Magnetometer network, comparison to visual auroral oval and exploitation of IL and IU indices Electron precipitatio n from KAIRA, comparison to model results Ionospheric D region cosmic noise absorption using riometer network and KAIRA observations UT3 IRAP node: PlasmasphereIonosphere Thermosphere modelling Operated by UT3-IRAP, Toulouse, France Validation of the IRAP Plasmasphere-Ionosphere Model (IPIM) results especially during solar eclipses, solar flares, CIRs or CMEs, using data from ionospheric stations, SuperDARN radars and GNSS satellites signals; Quantification of Joule heating and energetic particle precipitation heating at auroral latitudes through IPIM modelling fed with realistic inputs such as SuperDARN convection, satellites particle precipitation; Assessment of the thermosphere characteristics during perturbed periods (CIRs, CMEs) and their effect on the IPIM ionosphere modelling at high and middle latitudes. Comparison with ionospheric observations (ionosondes, EISCAT radars ). ROB GNSS node: GNSS hardware calibration and data processing facility Operated by the ROB GNSS group, Brussels, Belgium Adaptation of the ROB-IONO software process global data. Post-processing and nowcasting products on vTEC and sTEC at ionospheric pierce points. Test for Galileo inclusions in the processing Multi-GNSS comparison to test interoperability of the different systems. GNSS hardware delay estimation 3086 1. ware. In this framework, specific activities have already been carried out in PITHIA-NRF nodes to promote the networking concept and the design of new scient ific services based on the needs expressed by the scientific/engineering community and by the space industry. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Table 1 (continued) PITHIA-NRF nodes Indicative research topics for implementation by scientific users UPC IonSAT node: Precise GNSS modelling for new scientific and technical applications. Operated by UPC IonSAT group, Barcelona, Spain Global Tomographic modelling of the ionosphere computed with multifrequency GNSS phase-carrier observations. Electron density profiles derived from LEO based GNSS radiooccultation measurements. GNSS-Ionosphere Measurement of Extreme UltraViolet (EUV) solar flux variation during solar flares OE node: HF Digisonde-to-Digisonde (D2D) experiments Operated by OE, Roquetes, Spain HF D2D experiments to improve ionospheric specification in west Europe. Identification and specification of Large Scale Travelling Ionospheric Disturbances (LSTIDs). Identifica tion and specification of Plasma Depletions by means of GNSS data. Solar flare absorption effects on radio signals. IAP node: Ionosphere-lower atmosphere coupling, Operated by IAP, Prague, Czech Republic Analysis of wave coupling processes and consequences in the whole atmosphere and ionosphere using CDSSs and European Digisonde network measurements Validation of medium scale TIDs detection techniques Ionosphere/gravity wave climatology Troposphere - upper atmosphere - solar wind coupling studies exploing atmospheric electricity, ionosphere and solar wind data INGV node: ionospheric irregularities: specification, modelling and mitigation Οperated by INGV, Rome, Italy Ionospheric scintillations: Monitoring, modelling, forecasting and climatological analysis. Mitigation algorithms/techniques for HF. communications (Ray tracing) and for ionospheric scintillations on high accuracy positioning (PPP, NRTK) and Synthetic Aperture Radar Imaging; Ionospheric correction for augmentation systems in challenging areas (high and low latitudes). DLR-SO node: Space weather impact in the ionosphere and plasmasphere and mitigation of the effects Operated by DLR, Neustrelitz, Germany Solar flare monitoring and analysis of the ionospheric response. Impact analysis for HF communication and GNSS performances by combination with GNSS measurements (TEC, TEC rates) Spectral analyses to study radiation impacts on the lower ionosphere Research and analysis of D-Layer ionosphere disturbances from below (Gravity waves, Earthquakes, Hurricanes, radiation sources) Analysis of ionospheric response during Solar Eclipse events Cross correlation with external data sets from users (e.g. in the domain of GNSS-positioning or communication) to check the vulnerability of their systems to solar flare events Specification of topside ionosphere and plasmasphere electron density using NPSM The objectives and some results from selected TNA projects, organised in four research areas, are summarised here below: 2.3.1. Multi-instrument data analysis for detection and modelling of ionospheric storm effects and irregularities The majority of projects belonging to this group address topics relevant to the analysis of multi-instrument data for the study of the coupling of the lower atmosphere with the ionosphere, the coupling of the bottomside and topside ionosphere and the detection of upper atmosphere disturbances triggered by earthquakes, solar storms and solar flares. 3087 Upward Propagating Gravity Waves in the lower an d middle ionosphere (UPGW) Gravity waves (GWs) are an important class of atmospheric waves that can propagate from the troposphere up to the upper atmosphere, where they can contribute significantly to dynamical changes in the ionosphere. The aim of the UPGW project was to gain a deeper understanding of the coupling between the lower and the middle ionosphere via gravity waves by the concurrent analysis of narrowband VLF (characterising GWs in the lower ionosphere), continuous HF Doppler (characterising GWs in the middle ionosphere) and lightning data provided by the World Wide Lightning Location Network (WWLLN). Thereby, the research is expected to contribute to a better understanding and mitigation of the distorting effects of atmospheric waves on satellite communications and global GNSS-based positioning. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 The project aims at investigating the simultaneous occurrence of GWs in the lower ionosphere and in the F layer, by studying the nighttime ionosphere using narrowband VLF measurements (characterising GWs in the E layer) carried out at Tihany, Hungary and the multipoint and multi-frequency continuous Doppler sounding system, characterising GWs in the F layer (Chum et al., 2023) operated by the Institute of Atmospheric Physics, Czech Academy of Science (IAP Node). Due to the oblique propagation of GWs, multiple VLF propagation paths are analysed (Fig. 3) to find the path where the occurrence of GWs shows the highest correlation with the detection of GWs by the Doppler system. The goal is not to identify strictly the same GW in the lower ionosphere and in the F layer, but to explore the statistical relationship between the occurrence of GWs in the two ionospheric regions. 2. Characterization of Plasma Depletions and Effects on Geodetic Applications (CPD&EGA) In this work, local features of the ionosphere are identified, monitored, and characterised from ionosonde measurements at Ebro Observatory, satellite ultraviolet imag es from Special Sensor Ultraviolet Spectrographic Imager (SSUSI), total electron content (TEC) index (ROTI) (Pi et al., 1997) from GNSS, and all-sky 630 nm images at Oukaı ¨meden Observatory (Morocco). This TNA project is implemented in the OE node. The dynamics and coupling processes of plasma deplet ions in relation to upper atmosphere and space weather conditions are studied for the geomagnetic storm of 28 February 2014. This work verifies that ionosonde, satellite UV imaging, GNSS-ROTI, and all-sky imaging data can be combined to investigate and characterise ionospheric plasma depletions at local and regional scales (Calabia et al. 2024). In this scheme, the low latitude plasma depletion that appeared in Spain during the geomagnetic storm of 27 February 20 14, is investigated and characterised (Fig. 4); its variations in space and time are interrelated with the different multi-instrument data. 3. Comparisons and validation of the TIDs occurrence in the ionospheric tilt measurements with the GNSS observations (CVTIDs) Fig. 2. PITHIA-NRF TNA choices. 3088 Fig. 3. Map showing the different geophysical measurements to be used in the project. The orange triangle indicates the location of the continuous Doppler sounding system (Czech Republic), while the blue square indicates the location of the narrowband VLF receiver system (Tihany, Hungary). Red circles mark military VLF transmitters, which are connected to the Hungarian VLF receiver by dotted lines. The main objective of this project is to compare the capabilities and limitations of various observational techniques for studying MSTID over the European sector. Furthermore, these techniques will be used to quantify the causes and sources o f MSTIDs and to identify the potential indicator for developing the MSTID forecasting. To attain the main objective, the following specific objectives are proposed: Compare and validate the ionospheric tilt measurement results with the GNSS-dTEC estimated MSTIDs and explore the physical reasons relating ionospheric gradients with ionospheric tilt. Quantify the role of Es and F region coupling on the generat ion of TIDs under inter-hemispheric perspectives. The project is under implementation in the OE node. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Fig. 4. Left panel shows the ionogram from El Arenosillo Observatory (EA036), Spain, for 27 February at 21:00 h UTC, where range spread F reveals the presence of a plasma depletion. Right panel shows an all-sky OI 630.0 nm image captured at Oukaı ¨meden Observatory (OO), Morocco, on 27 February 2014, where spatial characteristics of the plasma depletion can be observed. 4. Longitudinal differences in travelling ionospheric disturbance charact eristics at middle latitudes (LONG) Thanks to the TNA programme, two groups of researchers from the Ionosphere Institute (Kharkiv, Ukraine) and the Institute of Atmospheric Physics, Czech Academy of Science (IAP Node), using a combination of various radiophysical methods studied ionosphere dynamics above Europe during the 22–24 September 2020 moderate geomagnetic storm. The results obtained in the project allow us to expand our knowledge about the regional characteristics of TIDs and improve the prediction capabilities of ionospheric models. Three ionosondes located in Juliusruh, Pruhonice and near Kharkiv, and the Kharkiv incoherent scatter radar were employed to study temporal and spatial TID signatures in ionospheri c F2 peak density and height and electron density variations at the heights of 100–300 km (Fig. 5). TIDs were observed during enhancemed auroral activity and local sunrise terminator passage and the following specific characteristics were recorded: diurnal occurrence at each location, predominant period, vertical and horizontal phase velocity and wavelength, relative amplitude of electron density fluctuations and propagation direction. With increased storm intensity day-to-night variations of hmF2 and NmF2 increased at all three sites (Panasenko et al., 2023; Aksonova et al., 2024). Fig. 5. Kharkiv incoherent scatter radar (on the left) and location of the instrumentation involved in the analysis (on the right). 3089 5. Wave-like structures in the ionosphere between Athens and Sopron (WIONAS) Travelling Ionospheric Disturbances (TIDs) detection software codes and relevant data collections, provided by the NOA node, have been exploited by the WIONAS project to identify wave structures propagating within the ionosphere above the South-East European region, in the area between Sopron and Athens Digisonde stations. Ionosonde measurements, including ionograms and Digisonde-to-Digisonde TID observations between the two Digisonde stations were analysed. Based on the data availability from the two Digisonde stations, some recent geomagnetic storms and lower atmospher e dynamic events were selected for further study. TID results from the TechTIDE database (Belehaki et al.,202 0) obtained from Digisonde measurements, and HF Interferometry method (based on the spectral , analysis of the MUF) and the GNSS gradient method, were analysed to obtain information about different triggering sources of the observed TIDs and their propagation characteristics. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Fig. 6. Diurnal nighttime spread F occurrence over Ebro for (a) 2014, (b) 2019 and (c) 2022. 6. Height-time-intensity (HTI) application and validation in TID and Es signatures on ex tended datasets (HAVES) HAVES has three main objectives, nighttime spread F characterization over the Ebro Observatory (OE), comparison of two methods to detect LSTIDs the HF-INT (Altadill et al., 2020) and the HTI (Haldoupis et al., 2006), and a long-term study of intermediate descending layers (IDLs). The project is implemented in the OE node. The first objective, the characterization of nighttim e spread F, was based on an extended ionogram dataset recorded by the OE digisonde during the interval 2012–2022 (Fig. 6). These ionograms were analysed to identify nighttime spread F events and evaluate any seasonal and solar activity trends. Clear seasonal characteristics and yearly inverse solar activity spread F dependence was identified. The second objective, LSTID activity over OE has been studied in terms of the HF-INT and HTI techniques (exploiting ionograms at a 5-min resolution recorded from 2016 to 2022). Similarities and differences in the diurnal LSTID occurrence were noted over Ebro as extracted by these two different techniques. The third objective of HAVES was a long-term study of intermediate descending layers (IDLs) over OE by applying the HTI methodology. 7. Validation AND Assessment of near-real time detection and f orecasting of LS-TIDs in Europe (VANDALS-TIDE) The main scientific purpose of the project is to study specific LSTID activity to validate and assess the methods of the detection and forecasting of LSTIDs and define potential early indicators of LSTID activity. LSTID detection and forecasting products will be cross validated with analysis of independent data providing clear TIDs signatures. As part of the validation process, the forecasted events need to be compared with measured data like HFINT, detrended Total Electron Content (dTEC), detrended isodensity contours (dNe(h)), and D2D products (from Digisonde measurements) over Europe. The project is under implementation in the OE node. 3090 8. STorm-related Study of Ionospheric iRRegularities over southern Europe using digisondes and GNSS Data (STIRRED) STIRRED aimed at highlighting some of the characteristics of the ionosphere by studying irregularities during disturbed geomagnetic conditions, focusing on southern Europe at geomagnetic latitudes of 35°󠇣-40°󠇣. Specifically the objectives deal with the investigation of Spreadoccurrence F in ionograms from El Arenosillo, Roquetes, Gibilmanna, and Athens ionosondes; and the study of TEC and ROTI behaviour from GNSS receiver networks in the Iberian Peninsula, Morocco, Italy, and Greece during geomagnetic storms. Additionally, the evolution of the Equatorial Ionisation Anomaly (EIA) during selected geomagnetic storms using data from global ionosphere maps of TEC (GIMs) has been addressed, to correlate observations of Spread-F, TEC, and ROTI with EIA evolution. The project’s scope extended beyond the analysis of a few specific storms, with plans to expand the study to include storms of varying intensities occurring at di fferent Universal Time (UTC). By assessing the ionosphere effect signatures in latitude, longitude, and local time, the project aims at providing insight into the broader impact of geomagnetic storms on the ionosphere above southern Europe. STIRRED project was implemented in the INGV node. Irregularities observed during several storms occurred in 2014, characterised by high solar activity, appear to be linked to the limited northward extension of the EIA during the storm’s main phase, as evidenced by GIMs. This localised expansion of the EIA underscores the importance of monitoring this area during storm phenomena to better understand its specific effects. Irregularities observed during several storms occurred in 2021, occurring during a period of low solar activity, could be attributed to Perkins instabilities, involving irregularities propagating from low to middle latitudes within discrete longitude sectors. This finding resonates wi th previous research in the North American sector. An example of the ROTI analysis for the 2021 storm is given in Fig. 7. of their profiles. This monitoring can be processed in real time, at any latitude, provided a clear sky. It will therefore constitute a useful technique for monitoring and predicting the state of the ionosphere, particularly (but not exclusively) for HF communications in the frame of space weather. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Fig. 13. The 3 polarimeters used in the CEP project study 3rd of March 2022. 2. Can PolaRISation Measurements of Auroral emissions Trace the Ionospheric Currents? (PRISMATIC) A group of researchers at the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) led by Herve ´ Lamy developed an imaging polarimeter called PLIP (Polar Lights Imaging Polarimeter), presented in Fig. 14. It measures the Degree of Linear Polarisation (DoLP) and the Angle of Linear Polarisation (AoLP)) of the three main auroral emissions (green, red and blue) within a large field of view. With this instrument, one goal is to check if there is a link between the AoLP of the auroral emission lines and the directions of field-aligned and/or horizontal ionospheric currents. 3097 Fig. 14. The PLIP instrument used in the PRISMATIC project. To achieve this objective, the BIRA-IASB team requested complementary observations from the EISCAT node, to compute a 2-D reconstruction of field-aligned electron fluxes. This was possibl e using data from the ALIS_4D optical network and measurements from the UHF antenna of EISCAT in Tromsø, Norway. Thanks to the TNA of PITHIA-NRF, they obtained 8 h of observations with EISCAT during a 10-day observation campaign with PLIP located at the Skibotn Observatory in Norway in November 2022. During this campaign, they received support from the EISCAT team who operated the necessary measurements with their infrastructure. PLIP data are still being analysed, but the authors made an interesting observation: a strong decrease of DoLP and a clear rotation of AoLP occurred during the main phase of the geomagnetic storm clearly identified by groundbased magnetometer data from Tromsø and UHF radar data from EISCAT. The origin of this polarisation is still puzzling and could be related to ionospheric currents, either field-aligned or horizontal Pedersen/Hall currents. Additional work must be done to confirm these results and see if AoLP of auroral emission lines can become a tracer of ionospheric currents. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 3. Study on ionospheric disturbances due to Space Weather in LOFAR data (iono-SW-LOFAR) The iono-SW-LOFAR project, implemented in the LOFAR node, considered establishing a correlation between solar flares and the ionospheric response seen by the LOFAR telescope. This is not only interesting from a scientific perspective, but it also forced us to make the data and metadata more accessible. Two larger databases, all solar flares since 2013 on the one hand and the available LOFAR scintillation data on the other, needed to be crossmatched. Unfortunately, no common data were found for the brightest, X class, solar flares. But some intriguing correlation was found for the less bright events. This will lead to a follow-up study and a stronger collaboration between solar and ionospheric physics in the future. 4. Use of LOFAR data for ionosp heric studies (ScintLO) This TNA project, also implemented in the LOFAR node, was more focused on teaching external users how to extract ionospheric information from the LOFAR stations, specifically from all sky imaging capabilities of the station. In this TNA project support for two researchers to visit Astron was provided. The ultimate goal of the project, to establish a metric that could be used for dynamic scheduling of LOFAR, was not fully met. But satisfactory progres s was made, new techniques developed, and the idea of using all sky imaging to determine the ionospheric state relevant for LOFAR observations is now being investigated further. The all-sky images are currently not considered as part of the e-Science Centre, but this could certainly be considered in the future. 5. Radio scintillation studies for prospects of space weather forecasting and analyses (RadioScint) The aim of the RadioScint TNA project is to determine if the methodology from Grzesiak et al. (2022) can be applied to a broader range of scintillation observations, specifically interplanetary scintillations (IPS). The described method uses multiple LOFAR station observations for ionospheric analysis. Scintillation measurements of specific radio sources are used to estimate ionospheric drift velocities and characterise the anisotropy of ionospheric irregularities. On the other hand, by observing a compact radio source ( 0.1 ) using a radio telescope, it is possible to determine the velocity with spectral analysis tools and density changes that are related to the changes in electron-density fluctuations (DNe) in the interplanetary medium. IPS data can be analysed using LOFAR singlesite and multi-site observations (e.g. Chang et al., 2019). RadioScint will look into adapting the method proposed and described by Grzesiak et al. 2022 to datasets obtained in the LOFAR IPS campaigns and the possibility of calculating solar wind velocity estimates (Fig. 15). The project involves cross-comparing outputs from single-site and cross-correlation analyses for specific case studies or previous LOFAR campaigns for both methods. If successful, further plans can be developed to assess this approach for space weather purposes as a follow-up activity to the current project. 3098 Fig. 15. Illustration of the scattering by a screen. From Grzesiak et al. (2022). 2.3.4. Calibration of n ew instruments 1. Study of the characteristics of ionospheric irregularities at high and low latitudes through coordinated observations of EISCAT and VHF Radar at Haringhata, India (CROLHL) The University of Calcutta is developing a high power fully active phased-array radar at 53 MHz at Haringhata, India, situated near the northern crest of the Equatorial Ionisation Anoma ly (EIA). The location of this radar is unique being the only one at this frequency in the southeast Asian longitude sector. Within the framework of the PITHIA-NRF TNA programme, the University of Calcutta ST Radar team was given access to the EISCAT node, with training about the EISCAT radar systems through regular online sessions. This team consists of seven people led by professor Ashik Paul. The training contained an introduction to the system, data formats, analysis methods and some interpretation of the radar data, and it was performed from April until September 2022. A number of sessions were organised. After the initial few meetings, the focus was on a couple of specific cases of space weather impact on the ionosphere. For these cases the University of Calcutta project team conducted computationally intensive data analysis using data from the EISCAT radar systems as well as satellite data from different latitude sectors. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 This project was the first step in the training process. It is followed by physical access, conducting coordinated experiments using the EISCAT UHF and University of Calcutta VHF radars, in September 2024. The University of Calcutta ST Radar (CU STR) project team has gained immensely from the online training provided by the EISCAT node. Since CU STR is a new facility being established in an Indian University with limited resources, availability of online resources initially and physical access in future will be extremely helpful in advancing the studies of ionosphere using the radar, a topic in which EISCAT is a global leader. 2. Estimating ionospheric irregularity layer height and drift velocity with GNSS and incoherent scatter radar (IILHV) The project is implemented in the EISCAT node and aims to increase the understanding of radio signal scintillation at high latitudes due to high-latitude ionospheric irregularities. A major uncertainty in current modelling and simulation efforts to understand ionospheric plasma instability mechanisms is due to the choice of input parameters regarding plasma drift speed and irregularity layer height and thickness. The project studies the high-latitude irregularity dynamics using a spaced GNSS receiver network in Svalbard, Norway, in c onjunction with the EISCAT ESR incoherent scatter radar. The primary objective is to apply the spaced receiver technique to four receivers from different institutes located in Ny-Alesund and test the feasibility of determining the plasma drift speed and height of the irregularity, using the incoherent scatter radar observations to verify the results and quantify the error. 3. Assessment of the ionospheric scintillation ov er Portugal (ALERT) The ALERT project was implemented in the INGV node. The team possesses approximately four years of continuous ionospheric measurements taken in Lisbon and spanning between November 2014 and February 2019. These measurements were conducted using a GNSS receiver equipped with SCINDA software, yielding 1-minute data including TEC, scintillation indices such as S4 and ROTI, as well as satellite elevation and azimuth angles. However, since the receiver was not calibrated upon installation, the accuracy of its measurements requires verification, possibly through comparison with data from nearby receivers. The objectives of ALERT concerned mainly the validation of the scintillation dataset from the Lisbon receiver to ensure accuracy and reliability. Additionally, a potential incorporation of those validated data into the INGV database, will enhance the collectiv e scintillation monitoring capabilities. Lastly, scintillation events that occurred at middle latitudes in both Portuguese and Italian regions have been investigated, particularly during geomagnetic storms, with the objective to understand regiona l variations and dynamics. 3099 As a result of the project, it was decided that site characterization and data validation procedures would be implemented for the Lisbon receiver dataset. Regrettably, upon examination, it was discovered that the data originated from a geodetic GNSS receiver equipped with SCINDA software operating at a 1-minute cadence. This receiver exhibits distinct design and data quality acquisition characteristics compared to the receivers available in the eSWua database, which are Ionospheric Scintillation Monitor Receivers (ISMRs) with different operational features. A scintillation event that occurred on June 22–23, 2015, was selected as a case study. Results of the analysis of this event are shown in Fig. 16. It displays the S4 variation over time recorded by the Lisbon scintillation receiver during June 22–23, 2015 and the related azimuth-elevation distribution, highlighting the region of enhanced scintillation. The related study has been presented during the European Space Weather Week 2023 in Toulouse and the URSI ATRASC 2024 meeting in Gran Canaria. 4. Caribbean Netherlands TEC measurement validation (CaNeTEC) The project focused on collaboration between KNMI researchers and the INGV node to enhance understanding and capabilities in ionosphere measurements. The primary aim was to compare KNMI’s GNSS receiver data in the Caribbean (Saba and Sint Eustatius stations) with ionosphere measurements from INGV and DLR. This comparative analysis aimed to comprehend calibration techniques and reproduce Total Electron Content (TEC) measurements from RINEX data files. Utilising INGV’s calibration software, validation of KNMI’s receiver output was achieved, leading to the attainment of initial scientific results. Notable observations included ionospheric disturbances caused by the Tonga volcanic eruption an d the response to a solar flare. KNMI initiated sharing scintillation data with INGV, enhancing the global coverage of the latter’s network. The project also discussed the potential benefits of integrating KNMI receivers into an international network, facilitating easier access to ionospheric observations for researchers. The project aimed also to establish a dedicated research group at KNMI, fostering long-term engagement and collaboration within the upper atmosphere research community. Calibration of GNSS receiver output using INGV’s TEC calibration software yielded promising results, with good agreement observed between measurements from Saba and Sint Eustatius stations and INGV and DLR TEC maps. An example of this is given in Fig. 1 7, which reports the vTEC measurements directly above the GNSS receiver at Saba (green) compared to INGV (blue) and DLR (orange) TEC maps evaluated at the receiver location over a period between 11 January and 19 January 2022 UTC. This specific case serves to highlight a case in which discrepancies were found, which deserve furt her investigation to be conducted outside the CaNeTEC project. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Fig. 16. (top) Time variations of S4 recorded by the Lisbon scintillation receiver during June 22–23, 2015. Letters A-D mark several scintillation subevents that took place during the night of June 22–23. (bottom) Azimuth-elevation distribution of S4 during June 22–23, 2015. The colour code indicates the range of elevation angles of the observations. The assessment of scintillation data produced by the receivers revealed no unexpected results, with discussions focusing on nuances such as the fixed cut-off frequency used in the equipment. Overall, the project facilitated rapid progress in KNMI’s research activities, including practical aspects such as data integration and knowledge sharing. 3. PITHIA-NRF metadata Schema and ontology PITHIA-NRF metadata are registered in the PITHIANRF e-Science Centre (see section 4) by the data providers. Descriptions of Resources are written as Extensible Markup Language (XML) documents that comply with three governing requirements: 3100 The PITHIA-NRF Schema, that controls the organisation of the registration documents: The Schema is based on the International Standards Organization (ISO) 19,100 series of standards for geographic infor mation, particularly 19156:2011 ‘‘Observations and Measurements”(O&M) standard; ISO 19156:2011 was adapted and extended for the space physics domain by the data model team of ESPAS (Near-Earth Space Data Infrastructure for e-Science) European Commission FP7 project, during its 2014-2017 active period (Belehaki et al., 2016); The ESPAS Schema has been adapted, simplified, and extended for PITHIA-NRF to meet specific project requirements. The PITHIA-NRF Ontology, that controls the standard vocabulary of terms specific to the domain of space physics: Fig. 17. Vtec measurements directly above the gnss receiver at saba (green) compared to ingv (blue) and dlr (orange) tec maps evaluated at the receiver location over a period between 11 january and 19 january 2022 utc. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 The Ontology is based on the original ESPAS Ontology design (Galkin & Belehaki, 2017), with extensions specific to PITHIA-NRF datasets and models. The XML Syntax, that controls formatting of registration documents per Wo rld Wide Web Consortium (W3C) definitions. Registration of new metadata in PITHIA-NRF is described in more detail in section 4.1. 3.1. PITHIA-NRF schema The ISO 19156:2011O&M standard provides the following core properties for an observat ion (or a computational model that predicts an observation): Feature of Interest: a real-world object that carries the property which is observed or modelled to produce a Data Collection, such as the Earth’s ionosphere; Observed Property: description of a physical Phenomenon obtained by means of observation or modelling that generat es an estimate of its Measurand value, such as critical frequency; Phenomenon is a physically observable entity; the top-level Phenomenon categories are Particle, Field, and Wave; Measurand is the quantitative or qualitative attribute of the Phenomenon to be evaluated, such as velocity, flux, density, etc. Result: data generated by the act of observation or modelling; Procedure: a sequence of Acquisitions and Computations that lead to a Result. The ESPAS Schema provides a significant extension to the ISO O&M standard needed to describe space physics observations in detail, and particularly to allow each Observation result to be registered with its individual Phenomenon Time, Spatial Extent, and parti cular subsets of Procedure as well as Observed Properties that were used during the Observation. 2 https://esc.pithia.eu/. 3101 The PITHIA-NRF Schema underwent a significant simplification of the ESPAS design. To improve its scalability to collections of multi-million observations (that would each have required an individual metadata registration document), the PITHIA-NRF Schema introduced a new concept of Data Collection, that captures the exhaustive set of possible Procedures’ Acquisition and Computation components, with all possible Observed Properties, and all Platforms that host the registered sensor Instruments. Thus, the PITHIA-NRF Schema omits the specifics of each individual Observation act, including their Phenomenon Time, Spatial Extent, and used components of Procedure. This simplification has delegated all functionality of data search by coincidence or conjunction to the original data providers, who remain responsible for the service functions that respond to incoming queries for temporal and spatial availability of data in the Data Collections. Instead, the PITHIA-NRF Schema adds a new Resource Catalogue for registration of Data Collection subsets of interest in a specific underly ing physical event, investigation, or academic publication. Only Data Collections registered in PITHIA-NRF can contribute to Catalogues. The Catalogue data subsets are provided with particular Phenomenon Time and Spatial Extent descriptions, as well as a standard Digital Object Identifier (DOI) to meet FAIR requirements. 3.2. PITHIA-NRF ontol ogy Most of the PITHIA-NRF Ontology definitions are the original RDF (Resource Description Framework) documents developed by the ESPAS ontology team. As the PITHIA-NRF data registration proceeds, new terms and definitions are added to the Ontology that were not required previously. The most active areas of such extensions are Computation Type, Phenomenon, and Dimensionali ty vocabularies to describe data collections generated by models and sensors that were not available in ESPAS. The Space Physics Ontology option in the e-Science Centre offers dynamic browsing of the ontology, allowing scientific users to find definitions for terms in the ontology, and understand how the various term s relate to each other. This is a very important function as all the registered metadata relate to each other based on ontology terms. 4. The e-science centre In addition to the 12 nodes that provide access to research infrastructures, the PITHIA-NRF e-Scie nce Centre (eSC 2 ) is established as a central service that enables without the requirement to log in and allows any user to: registration of, access to and use of Data Collect ions, Catalogues and Workflows. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Data collections can be either sets of raw or processed observations, offe red by providers inside or outside PITHIA-NRF. Catalogues are smaller sets of data that describe a certain event, or set of events, related to, for example, a publication. Data Collections can be live and changing/growing constantly. Catalogues refer to fixed sets of data that can also be assigned a DOI and referenced in scientific publications to support reproducibility. Workflows are a combination of already registered models where the output of one model can be fed to other models as input, and the execution is automated. eSC services are organised in five main categories, as illustrated in Fig. 18. The bottom box of Fig. 18 shows the various Security Services, such as authentication, authorisation, data protection and privacy management. These services are essential and required, and provide the basis for the other, higher-level services. On top of the Security Services, the e-Science Centre provides the User Account Management services. While access to most material and resources is open in the PITHIA-NRF eSC a specific User Account Management is necessary for establishing and managing accounts of some user groups (e.g., Data Collection owners and eSC administrators). PITHIA-NRF e-Science Centre users are presented with three main categories of services: Information and Community Services, e-Learning Services, and Scientific Services. Information and Community Services provide mainly static information about the commun ity in the form of news items or blogs, but this service category also incorporates more dynamic services that enable networking and collaboration between scientists or even with the general public. E-Learning Services provide access to learning and research material in an organised and systematic way. PITHIA-NRF e-Science Centre users are able to search for learning and research material based on an associated ontology, and could design and create learning graphs and paths that make them better understand and follow the various scientific and technical concepts associated with the resources of the e-Science Centre. Fig. 18. PITHIA-NRF e-Scienc e Centre Services. 3102 Finally, Scientific Services allow users to access eScience Centre resources, namely Data Collections and Catalogues. Such resources are published by resource owners (i.e. Data Collection and Catalogue owners) using a rich set of metadata, and made available for scientific users to search, find and utilise them based on their scientific goals and requirements. Users will also get access to a general helpdesk and ticketing system https://ggus.eu/, which is especially important if questions arise when access ing Data Collections or executing Models. The eSC is under constant development, and the roadmap has been set for adding new features and functionalities. At the time of writing this article, the eSC offers three main functionalities. Its home page is shown in Fig. 19. The three main categories of functionalities are: 1. The Search & Browse category is accessible to Users Search for Data Collections by specifying a selection of ontology terms, or by simple freetext search. ; Browse all registered Data Collections. Browse all registered Catalogues. Browse all registered Metadata related to the twelvestep registration process. Fig. 19. E-science centre home page. The 2nd and 3rd blocks under Data Registration are only visible to authenticated users upon login. 2. The Space Physics Ontology category allows any User to: A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Search for terms and their definitions. Access the Space Physics Ontology Guide. 3. The Data Registration category allows: Any user to access and download the de tailed Data Resource Registration Guide. Authenticated users (after logging in) to register new Data Col lections through associated XML-based metadata. Authenticated users to modify or delet e existing Data Collections. Additionally, the XML schemas, which may be of interest to advanced users, are also available in this category after authentication. The first official prototype was released in May 2023 with the functionalities detailed in this document. Recently the second protototype was released. This second prototype provides full user management capabilities and the implementation of further Data Collection execution methods. Additionally, most Data Collections are accessible via one or more interaction methods (see section 4.2). During the final year of the project the implementation of advanced services (workflow capabilities and machine learning algorithms) will be investigated and impl emented as appropriate. 3103 4.1. Registration and management Registration of new PITHIA-NRF metadata is accomplished by submitting XML documents to the eSC portal, where all documents are validated against the governing requirements of the PITHIA-NRF Schema, PITHIANRF Ontology, and XML Syntax. To access the hidden features (Data Collection and Catalogue registration, management and deletion functionalities) of the eSC user login is required. The additional functionalities available to authorised users are shown at the bottom of Fig. 1 9. The Data Registration group of functionalities focuses mainly on how Organisations and their Members can register metadata. Any member of an organisation validated by the eSC staff has the authority to register, update and delete metadata under the Register & Manage Metadata option. They can register Data Collections, Catalogues and Workflows, modify earlier registrations or delete unnecessary ones. Additionally, the Metadata Registration Guide is a document that explains the structure of the Metadata and how Organisations should create and regis- ter them in compliance with the PITHIA-NRF schema. Finally, the Metadata Models option presents all the schemas that each registration item is validated against before it can be registered. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 When a member of a validated organisation selects the Register & Manage Metadata option, the eSC offers three options: Data Collection-related Metadata, where one can manage registrations according to the twelve-steps registration process. Catalogue-related Metadata, where one can manage registration in the three Catalogue categories. Workflows, where one can manage the execution of interconnected data collections, usually via a single API. Data Collection – related metadata are registered following the sequence of twelve steps as shown in Fig. 20. All PITHIA-NRF data resources are registered with the eScience Centre using the International Standards Organisation guidelines for Observations and Measurements (ISO 19156: 2011). PITHIA-NRF leverages metadata designs for space physics data registration developed by the ESPAS consortium (Belehaki et al., 2016) in 2012–2015. During the active period of the PITHIA-NRF project, the governing ISO standards prescribe using XML as the physical format. While PITHIA-NRF data registrations are done using XML as the metadata format, some additional capabilities are offered with the addition of the interactive wizard. Fig. 20. Twelve steps of PITHIA-NRF data resource registration. Different colours are used to indicate the complexity of the definitions; blue ovals are harder to define. OP is Observed Property information commonly used for content-aware searches. The arrows denote dependencies (references) between steps. 3104 To facilitate the registration process, document templates are provided for each step. Each template is prestructured according to the PITHIA-NRF metadata model. Editing replaces the example content with resource-specific information. Such a template-based approach facilitates the registration process, with less likelihood of errors. However, to make the process fully robust, the eSC always goes through a set of comprehensive checks of every uploaded document. First, it checks the XML syntax for formal errors. Second, it assures that all XML documents are compliant with the defined XML schemas and the PITHIA-NRF ontology. Finally, it guarantees that all other XML documents that are referred to from the currently uploaded one do exist. In case of errors eSC notifies the user pointing to the origin of the problem. With this rigorous process, errors (except semantic errors that refer to the scientific content or logic) can be eliminated. Data resource registration is organised using the concept of the Metadat a Model and of the Domain Ontology: Metadata Model: ISO-controlled organisation of the metadata components and their relationshi ps in a generic, science-neutral manner; Domain Ontology: a vocabulary of physical concepts pertaining to a particular domain of science; usually structured and provided with wider-narrower relationships. Cloud A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 The PITHIA-NRF Space Physics Ontology for contentaware data collection registration with the PITHIA-NRF e-Science Centre is detailed in a guide available in the eScience Centre by Galkin (2023). Catalogues are listings of events or investigations assembled to aid users in locating data of interest. Each Catalogue entry has distinct begin and end times and an optional DOI to the Data Subset in a permanent storage. Catalogues are not part of the standard Data Collection registration. The catalogues are managed separately, based on the Data Collections in PITHIA-NRF eScience Centre. Only data registered in the eSC can be included in a catalogue. There are three types of components of each Catalogue: 1 Top-level Catalogue Category (e.g., Catalog_VolcanoE ruption) a. The Catalogue Category is ontology-controlled 2 Individual entries of the Catalogue describing each specific eve nt or investigation (e.g. HungaTonga_202201–15) b. Each entry has a description and PhenomenonTime c. Each entry is linked to the Catalogue Category document 3 Data Subset items (e.g. Ma nually Scaled Ionograms) a. Each Data Subset refers to a Data Collection b. Each Data Subset includes < resultTime > to define intervals of time that the subset spans c. Optionally, the data provider may specify a DOI for the persistent storage of the Data Subset DOI generatio n is directly supported by the eSC, but it can also be generated externally 4.2. Data collection inte raction methods One of the most important roles of the eSC is the provision of methods to enable interaction with models and observational data (Data Collections, DC). Such interactions enable scientists to execute a model on-demand, or retrieve, visualise and manipulate data from a dataset or an underlying database. As this is the ultimate aim of the eSC, it is important that the system caters for multiple options and requirements. In general, the implementation of each interaction method should be simple for the resource provider and as automated as possible. Four different interaction methods are supported in the eSC. Each Data Collection (DC) provider can decide which method they impl ement. It is essential to provide at least one interaction method, otherwise users cannot access the DC. For further flexibility, implementing multiple interaction methods is also supported. The currently planned interaction methods in the eSC are summarised below. The first two of these methods have already been implemented and integrated into the eSC. The last two methods are currently under investigation and prototyping. 3105 1. Get a link once the Data Collection is found This method is fully implemented and a natural part of the Data Collection registration process. In this method, the Data Collection provider registers a link to the Data Collection in the ‘‘linkage” field of the DC’s XML registration file. When a user finds a DC as a result of search or browse, the eSC displays this link based on the XML registration document. Once clicking on the link, the user is redirected to an external site/repository managed by the PITHIA-NRF partners in order to access and interact with the DC. The major advantage of this method is its simplicity. The provider does not have to do anything extra on top of the actual registration, and the DC, being maintained at the data provider organisation, is always up-to-date. However, the method also comes with shortcomings. As the link takes the user outside the eSC, all functionalities are reduced to the capabilities of the provider’s services. While this method allows users to find and discover Data Collections from the single entry point of the eSC, it does not provide further integration beyond this. 2. Execute Model within the e-Science Centre via API In this method the provider has to implement (if not already available) an API (ideally, following the OpenAPI standard https://www.openapis.org/) to execute a model or query/retrieve a dataset. Next, a machine readable YAML or JSON specification of this API needs to be created (or preferrably, generated automatically). Finally, this API specification needs to be registered in the eSC by simply providing a link to it. Using this specification, the eScience Centre automatically generates a graphical user interface to interact with the Data Collection. This method is also fully implemented in the eSC. This method provides much closer integration with the eSC than the first one. When a user interacts with the Data Collection, this happens from inside the eSC. The look and feel is the same for every application and as such it is easier for the users to get accustomed to it. On the negative side, the task of DC providers is significantly bigger. They need to assure that the Data Collection is accessible via a suitable API and they have to provide a formal specification of it (although, there are several software tools that automate this process). This may require significant development effort on the producer side, especially in case of legacy Data Collections. 3. Dynamically deploy Data Collection (Model) in the This method is not implemented yet and only a preliminary specification and a proof of concept exist regardi ng its realisation (Pierantoni, Kiss & Bolotov et al., 2022). The core of the idea is to take a containerised version of the Data Collection and deploy it dynamically ondemand in cloud computing resources (Kiss, Kacsuk & Kovacs et al., 2019). This scenario would require the Data Collection provider to containerise the application and then upload it to a suitable container repository (e.g. DockerHub 3 ). After this, the provider also needs to describe the Data Collection with a YAML 4 -based description file (Pierantoni, Kiss & Terstyanszky et al. 2020). When a user selects the DC, it gets deployed in the cloud and a copy of it is executed specifically for the user. Once it is not required anymore (e.g. execution terminates or the user decides to delete the service), it gets destroyed. The method is specifically suitable for models that can be deployed as a set of microservices and then executed. A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 The advantage of the method is its flexible execution in the cloud. Using cloud resources and only utilising these when necessary is scalable and cost effective. On the negative side, this approach requires the most expertise and effort from the provider. By interfacing the e-Science Centre and the dynamic deployer module with EGI, we can ensure deployability into 30 national/regi onal OpenStack clouds which are federated in the EGI Cloud Compute service. This network can give PITHIA-NRF and its users the possibility to select the national cloud resources for each user, lowering/eliminating the need for cross-national compute consumption. 4. Download and install Data Collect ion on local computer This method also has not been implemented yet while it requires only a minor effort. The idea is to package and make the Data Collection (typically a model) available for download and installation by the prov ider. The download happens through the eSC. Once users find the model via browse or search, they can download and install it in the local environment. The advantage of this method is its simplicity for all parties. However, on the negative side, it is only suitable for small models that are executable on the user’s local machine. In the next section a more detailed description of the second method is provided. As described it has already been implemented and provides a higher level of integration as compared to the first method. 4.3. Registration of scientific models via API The objective behind this interaction method is to provide Scientific Users with a Graphical User Interface (GUI) that offers homogeneous access to all Data Collections that have implemented an API. Most Data Collections have their custom GUI, which Scientific Users must learn before interacting with the Data Collection. There are also Data Collections without a GUI for access. These may come with a Command Line Interface (CLI), which Scientific Users must get access to and learn how to use. When an organisation registers a Data Collection by also providing an API, it provides the Scientific Users two benefits. When a Scientific User uses the API as an interaction method: 3 DockerHub https://hub.docker.com/. 4 5 YAML https://yaml.org/. Swagger UI https://swagger.io/tools/swagger-ui/. 3106 The eSC dynamically generates a GUI specifically dedicated to that Data Collection. For all Data Collections, the look and feel will be similar in the eS C, the only difference between the various Data Collections being that they will offer different options for available actions. The eSC will not redirect the user to any external source but will handle the communication with the Data Collection itself, and the Scientific User will stay in the eSC. Additionally, for those Data Collections that do not offer a GUI and are available only through CLIs, it is much simpler for the providers to create an API than to build a GUI, as they relieve themselves from creating and maintaining the custom views of the GUI. The tool that the eSC uses to produce the automa tically generated GUI is Swagger UI. 5 The source code of Swagger UI has been customised and integrated into the eSC in a dedicated Django Application that reads the API specification, creates the interface, and handles the communication with the Data Collection’s API. Fig. 21 below presents the two steps Scientific Users have to take to interact with an API. On the left hand side, the Scientific Users must select one of the search or browse options of the eSC and find the Data Collection they want to interact with. Suppose the Data Collection offers an API (right-hand side of Fig. 21), Scientific Users can click the link Open API Interface in new tab and the eSC will dynamically generate an interface. Following this, the Scientific Users can perform any of the available actions and conduct their scientific research by communicating with the Data Collection’s API. Several models are registered in the eSC using API as an interaction method. A list is provided below. The Drag Temperature Model 2020 is a semi-em pirical thermosphere model (DTM2020; Bruinsma and Boniface, 2021). BSPM (Belgian SWIFF Plasmasphere Model) is a 3DKinetic semiempirical model of the plasmasphere developed by the Solar Wind Division of the Royal Belgian Institute for Space Aeronomy (Pierrard and Stegen, 2008; Pierrard and Voiculescu, 2011; Botek et al., 2021; Pierrard et al., 2021 for the last version). The hmF2_qModel (Altadill et al., 2 013) calculates and predicts the ionospheric electron density peak height of the F2 region, hmF2, under quiet conditions. Table A1 (continued) A. Belehaki et al. Advances in Space Research 75 (2025) 3082–3114 Acronym Definition PITHIANRF Plasmasphere Ionosphere Thermosphere Integrated Research Environment and Access servi ces a Network of Research Facilities PLIP Polar Lights Imaging Polarimeter PPP Precise Point Positioning R&D Research and Develo pment RAEGE-Az Rede Atla ˆntica de Estac¸o ˜es Geodina ˆmicas e Es paciais Azores Association RDA Research Data Alliance RDF Resource Description Framew ork RELEC Relativistic ELECtrons RI Research Infrastr ucture RINEX Receiver Independent Exchan ge ROB Royal Observatory of Belgium ROT Rate Of Chance of TEC SAR Synthetic-Aperture Radar s SGO Sodankyla ¨ Geophysical Obser vatory SH Spherical Harm onic SMEs Small and Medium-sized Enterprises SSA Space Situational Aw areness sTEC slant Total Electron Content STIM Storm Time Ionospheric Model SWIF Solar Wind driven autoregression model for Ion ospheric short-term Forecast TDR Trusted Digital Repo sitory TEC Total Electron Content TIDs Travelling Ionospheric Dis turbances TNA TransNational Access TSAR Time Series AutoR egressive TSWC Tucuman Space Weather Center UHF Ultra High Frequency (300–3 000 MHz) UI User Interface UPC Universitat Polite `cnica de Catalunya UPCIonSAT UPC Ionospheric determination and navigation based on Satellite And Terrestrial systems URSI Union Radio-Scientific Internationale / International Union of Radio Science UT University of Twente, The Netherlands University Toulouse III-Paul Sabatier – Institut de Recherche en Astrophysique et Plane ´tologie UT3-IRAP UTC Universal Time UV UltraViolet VHF Very High Frequency (30–30 0 MHz) VLF Very Low Frequency (3–30 kHz) vTEC vertical Total Electron Content W3C World Wide Web Consortium WIONAS Wave-like structures in the IONosphere between Athens and Sopron XML Extensible Markup Lang uage YAML YAML Ain’t Markup Language 3113 References Altadill, D., Torta, J.M., Blanch, E., 2009. 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