Description: This work investigates physical mechanisms triggering phase scintillations on L-band signals under strong stormy conditions. Thanks to selected ground-based Global Navigation Satellite Systems (GNSS) receivers, located both in Antarctica and in the Arctic, an interhemispheric comparison between high latitude ionospheric observations in response to the peculiar solar wind conditions occurred on June 22, 2015 is here shown. To trace back the observed phase scintillations to the physical mechanisms driving it, we combine measurements from GNSS receivers with in-situ and ground-based observations. Our study highlights the ionospheric scenario in which irregularities causing scintillation form and move, leveraging on a multi-observation approach. Such approach allows deducing that scintillations are caused by the presence of fast-moving electron density gradients originated by particle precipitation induced by solar wind variations. In addition, we show how the numerous and fast oscillations of the north-south component of the interplanetary magnetic field (Bz,IMF) result to be less effective in producing moderate/intense scintillation events than during period of long lasting negative values. Finally, we also demonstrate how the in-situ electron density data can be used to reconstruct the evolution of the ionospheric dynamics, both locally and globally.

Description: Published

Description: GM454

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: We study ionospheric scintillation on GNSS signals at equatorial latitudes to draw a climatological picture of the low latitude ionosphere in the Brazilian sector during the ascending phase of the upcoming 2013 solar maximum. Such data have been acquired during the early stage of the CIGALA project (http://cigala. galileoic.org/), funded by the European Commission under the 7th Framework Program and the outcome of this work is part of the scientific achievements of the project itself. The considered network is based on the novel PolaRxS receivers, developed and deployed specifically to comply with the aims of the FP7 project. The PolaRxS is able to monitor ionospheric scintillation for all operational and upcoming GNSS constellations (GPS, GLONASS, Compass, GALILEO) and corresponding frequencies in the L-band. The ionosphere over the Brazilian territory, being close to the southern crest of the Equatorial Ionospheric Anomaly (EIA), is heavily affected by intense scintillation conditions. The sector under investigation is also very peculiar with respect to other low latitude regions, because of its proximity to the South Atlantic Magnetic Anomaly (SAMA). The application of the Ground Based Scintillation Climatology (GBSC) technique, for the first time simultaneously on GPS and GLONASS data and on both L1 and L2 frequencies, highlights the joint effect of the EIA and of the SAMA in producing the irregularities leading to scintillation.

Description: Published

Description: 199-206

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS (Global Navigation Satellite Systems) occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation of several aspects of GNSS system performance, including integrity, accuracy and availability. The two indices adopted worldwide to characterise ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalised by its mean value, and the phase scintillation index, rU, which is the standard deviation of the de-trended carrier phase. Collaborative work between NGI and INGV supports a permanent network of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers that covers a wide range of latitudes in the northern European sector. Data from this network has contributed significantly to several papers during the past few years (see e.g. De Franceschi et al., 2008; Aquino et al., 2009; Spogli et al., 2009, 2010; Alfonsi et al., 2011). In these investigations multipath effects and noise that contaminate the scintillation measurements are largely filtered by applying an elevation angle threshold. A deeper analysis of the data quality and the development of a more complex filtering technique can improve the results obtained so far. The structures in the environment of each receiver in the network which contaminate scintillation measurements should be identified in order to improve the quality of the scintillation and TEC data by removing error sources due to the local environment. The analysis in this paper considers a data set characterised by quiet ionospheric conditions of the mid-latitude station located in Nottingham (UK), followed by a case study of the severe geomagnetic storm, which occurred in late 2003, known generally as the “Halloween Storm”.

Description: Published

Description: 1237-1246

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: Ionospheric scintillation can seriously impair the Global Navigation Satellite Systems (GNSS) receiver signal tracking performance, thus affecting the required levels of availability, accuracy and integrity of positioning that supports modern day GNSS based applications. We present results from the research work carried out under the Horizon 2020 European Commission (EC) funded Ionospheric Prediction Service (IPS) project. The statistical models developed to estimate the standard deviation of the receiver Phase Locked Loop (PLL) tracking jitter on the Global Positioning System (GPS) L1 frequency as a function of scintillation levels are presented. The models were developed following the statistical approach of generalized linear modelling on data recorded by networks in operation at high and low latitudes during the years of 2012–2015. The developed models were validated using data from different stations over varying latitudes, which yielded promising results. In the case of mid-latitudes, as the occurrence of strong scintillation is absent, an attempt to develop a dedicated model proved fruitless and, therefore, the models developed for the high and low latitudes were tested for two mid-latitude stations. The developed statistical models can be used to generate receiver tracking jitter maps over a region, providing users with the expected tracking conditions. The approach followed for the development of these models for the GPS L1 frequency can be used as a blueprint for the development of similar models for other GNSS frequencies, which will be the subject of follow on research.

Description: Published

Description: A51

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: This paper presents how the magnetosphere-plasmasphere-ionosphere system was affected as a whole during the geomagnetic storm peaking on 27 May 2017. The interplanetary conditions, the magnetospheric response in terms of the magnetopause motion, and the ionospheric current flow pattern were investigated using data, respectively, from the WIND spacecraft, from GOES15, GOES13, THEMIS E, THEMIS D and THEMIS A satellites and from the INTERMAGNET magnetometer array. The main objective of the work is to investigate the plasmaspheric dynamics under disturbed conditions and its possible relation to the ionospheric one; to reach this goal, the equatorial plasma mass densities derived from geomagnetic field line resonance observations at the European quasi-Meridional Magnetometer Array (EMMA) and total electron content values obtained through three GPS receivers close to EMMA were jointly considered. Despite the complexity of physical mechanisms behind them, we found a similarity between the ionospheric and plasmaspheric characteristic recovery times. Specifically, the ionospheric characteristic time turned out to be ~ 1.5 days, ~ 2 days and ~ 3.1 days, respectively, at L ~ 3, L ~ 4 and L ~ 5, while the plasmaspheric one, for similar L values, ranged from ~ 1 day to more than 4 days.

Description: Published

Description: ID 77

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: This work presents a contribution to the understanding of the ionospheric triggering of L-band scintillation in the region over São Paulo state in Brazil, under high solar activity. In particular, a climatological analysis of Global Navigation Satellite Systems (GNSS) data acquired in 2012 is presented to highlight the relationship between intensity and variability of the total electron content (TEC) gradients and the occurrence of ionospheric scintillation. The analysis is based on the GNSS data acquired by a dense distribution of receivers and exploits the integration of a dedicated TEC calibration technique into the Ground Based Scintillation Climatology (GBSC), previously developed at the Istituto Nazionale di Geofisica e Vulcanologia. Such integration enables representing the local ionospheric features through climatological maps of calibrated TEC and TEC gradients and of amplitude scintillation occurrence. The disentanglement of the contribution to the TEC variations due to zonal and meridional gradients conveys insight into the relation between the scintillation occurrence and the morphology of the TEC variability. The importance of the information provided by the TEC gradients variability and the role of the meridional TEC gradients in driving scintillation are critically described.

Description: Published

Description: A36

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: Space weather events related to solar activity can affect both ground and space-based infrastructures, potentially resulting in failures or service disruptions across the globe and causing damage to equipment and systems. Global Navigation Satellite Systems (GNSS) represent one of such infrastructures that can suffer from electromagnetic phenomena in the atmosphere, in particular due to the interaction of the RF signals with the ionosphere. The Ionosphere Prediction Service (IPS) is a project funded by European Commission to provide a prototype platform for a monitoring and prediction service of potential ionosphere-related disturbances affecting GNSS user communities. It is designed to help these communities cope with the effects of the ionospheric activity and mitigate the impacts of these effects on the specific GNSS-based application/service. The IPS development has been conceived of two concurrent activities: the design and implementation of the prototype service and the research activity, which represents the scientific backbone of IPS and is at the base of all the models and algorithms used for the computation of the products. The products are the basic IPS output that translate the nowcasting or forecasting information from the whole IPS system down to the final user. They are fine-tuned to match the different needs of the communities (scientific, aviation, high accuracy, etc.) which the service is targeted to and to warn the GNSS users about possible performance degradations in the presence of anomalous solar and atmospheric phenomena. To achieve this overarching aim, four different blocks of products dealing with solar activity, ionospheric activity, GNSS receiver and system performance figures have been developed and integrated into a unique service chain. The service is available to a set of invited users since July 2018 through a web portal and its provision with all the necessary operations will last 6 months. The prototype will be also ported to the Joint Research Centre (JRC). This phase will be useful to further test the platform, and to assess whether and how a dedicated prediction service for International Technical Symposium on Navigation and Timing (ITSNT) 2018 13-16 Nov 2018 ENAC, Toulouse, France Galileo users is to be implemented as part of the service facilities of the Galileo infrastructure.

Description: Published

Description: 2A. Fisica dell'alta atmosfera

Description: 7SR AMBIENTE – Servizi e ricerca per la società

Description: N/A or not JCR

Description: The effect of the Earth’s ionosphere represents the single largest contribution to the Global Navigation Satellite System (GNSS) error budget and abnormal ionospheric conditions can impose serious degradation on GNSS system functionality, including integrity, accuracy and availability. With the growing reliance on GNSS for many modern life applications, actionable ionospheric forecasts can contribute to the understanding and mitigation of the impact of the ionosphere on our technology based society. In this context, the Ionosphere Prediction Service (IPS) project was set up to design and develop a prototype platform to translate the forecast of the ionospheric effects into a service customized for specific GNSS user communities. To achieve this overarching aim, four different product groups dealing with solar activity, ionospheric activity, GNSS receiver performance and service performance have been developed and integrated into a service chain, which is made available through a web based platform. This paper provides an overview of the IPS project describing its overall architecture, products and web based platform.

Description: Published

Description: A41

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: Many real-life signals and, in particular, in the space physics domain, exhibit variations across different temporal scales. Hence, their statistical momenta may depend on the time scale at which the signal is studied. To identify and quantify such variations, a time-frequency analysis has to be performed on these signals. The dependence of the statistical properties of a signal fluctuation on the space and time scales is the distinctive character of systems with nonlinear couplings among different modes. Hence, assessing how the statistics of signal fluctuations vary with scale will be of help in understanding the corresponding multiscale statistics of such dynamics. This paper presents a new multiscale data analysis technique, the adaptive local iterative filtering (ALIF), which allows to describe the multiscale nature of the geophysical signal studied better than via Fourier transform, and improves scale resolution with respect to discrete wavelet transform. The example of geophysical signal, to which ALIF has been applied, is ionospheric radio power scintillation on L band. ALIF appears to be a promising technique to study the small-scale structures of radio scintillation due to ionospheric turbulence.

Description: Published

Description: 1031–1046

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal

Description: ESPAS, the ‘‘near-Earth space data infrastructure for e-science” is a data e-infrastructure facilitating discovery and access to observations, ground-based and space borne, and to model predictions of the near-Earth space environment, a region extending from the Earth’s atmosphere up to the outer radiation belts. ESPAS provides access to metadata and/or data from an extended network of data providers distributed globally. The interoperability of the heterogeneous data collections is achieved with the adoption and adaption of the ESPAS data model which is built entirely on ISO 19100 series geographic information standards. The ESPAS data portal manages a vocabulary of space physics keywords that can be used to narrow down data searches to observations of specific physical content. Such content-targeted search is an ESPAS innovation provided in addition to the commonly practiced data selection by time, location, and instrument. The article presents an overview of the architectural design of the ESPAS system, of its data model and ontology, and of interoperable services that allow the discovery, access and download of registered data. Emphasis is given to the standardization, and expandability concepts which represent also the main elements that support the building of long-term sustainability activities of the ESPAS e-infrastructure.

Description: Published

Description: 1177–1200

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: 2A. Fisica dell'alta atmosfera

Description: JCR Journal