Luca Spogli

Space weather challenges of the polar cap ionosphere

This paper presents research on polar cap ionosphere space weather phenomena conducted during the European Cooperation in Science and Technology (COST) action ES0803 from 2008 to 2012. The main part of the work has been directed toward the study of plasma instabilities and scintillations in association with cusp flow channels and polar cap electron density structures/patches, which is considered as critical knowledge in order to develop forecast models for scintillations in the polar cap. We have approached this problem by multi-instrument techniques that comprise the EISCAT Svalbard Radar, SuperDARN radars, in-situ rocket, and GPS scintillation measurements. The Discussion section aims to unify the bits and pieces of highly specialized information from several papers into a generalized picture. The cusp ionosphere appears as a hot region in GPS scintillation climatology maps. Our results are consistent with the existing view that scintillations in the cusp and the polar cap ionosphere are mainly due to multi-scale structures generated by instability processes associated with the cross-polar transport of polar cap patches. We have demonstrated that the SuperDARN convection model can be used to track these patches backward and forward in time. Hence, once a patch has been detected in the cusp inflow region, SuperDARN can be used to forecast its destination in the future. However, the high-density gradient of polar cap patches is not the only prerequisite for high-latitude scintillations. Unprecedented high-resolution rocket measurements reveal that the cusp ionosphere is associated with filamentary precipitation giving rise to kilometer scale gradients onto which the gradient drift instability can operate very efficiently. Cusp ionosphere scintillations also occur during IMF B Z north conditions, which further substantiates that particle precipitation can play a key role to initialize plasma structuring. Furthermore, the cusp is associated with flow channels and strong flow shears, and we have demonstrated that the Kelvin-Helmholtz instability process may be efficiently driven by reversed flow events.

Formation of ionospheric irregularities over Southeast Asia during the 2015 St. Patrick's Day storm

We investigate the geospace response to the 2015 St. Patricks Day storm leveraging on instruments spread over Southeast Asia (SEA), covering a wide longitudinal sector of the low-latitude ionosphere. A regional characterization of the storm is provided, identifying the peculiarities of ionospheric irregularity formation. The novelties of this work are the characterization in a broad longitudinal range and the methodology relying on the integration of data acquired by Global Navigation Satellite System (GNSS) receivers, magnetometers, ionosondes, and Swarm satellites. This work is a legacy of the project EquatoRial Ionosphere Characterization in Asia (ERICA). ERICA aimed to capture the features of both crests of the equatorial ionospheric anomaly (EIA) and trough (EIT) by means of a dedicated measurement campaign. The campaign lasted from March to October 2015 and was able to observe the ionospheric variability causing effects on radio systems, GNSS in particular. The multiinstrumental and multiparametric observations of the region enabled an in-depth investigation of the response to the largest geomagnetic storm of the current solar cycle in a region scarcely reported in literature. Our work discusses the comparison between northern and southern crests of the EIA in the SEA region. The observations recorded positive and negative ionospheric storms, spread F conditions, scintillation enhancement and inhibition, and total electron content variability. The ancillary information on the local magnetic field highlights the variety of ionospheric perturbations during the different storm phases. The combined use of ionospheric bottomside, topside, and integrated information points out how the storm affects the F layer altitude and the consequent enhancement/suppression of scintillations.

Ionosphere monitoring in South East Asia: Activities in GINESTRA and ERICA projects

GINESTRA and ERICA are two projects funded in the framework of the ALCANTARA Initiative of the European Space Agency. GINESTRA is a survey which aims to explore the capabilities of ionosphere monitoring in South East Asia to identify both institutions involved in this field and existing monitoring facilities. ERICA exploits the GINESTRA outcomes and aims to characterize the ionospheric variability of the Equatorial Ionospheric Anomaly in the region, in particular the variation of the plasma electron density in the southern and northern crests of the anomaly and over the dip equator identified by the Equatorial Ionospheric Trough. To achieve this goal, an ad hoc measurements campaign is conducted with ground-based instruments located in the footprints of the Equatorial Ionospheric Anomaly and of the Equatorial Ionospheric Trough in Vietnam and Indonesia. The paper presents the outcomes of GINESTRA and highlights some preliminary results of the data analysis conducted so far in the framework of ERICA.

DemoGRAPE: Managing Scientific Applications in a Cloud-Federated Environment

There is a strong relationship between scientific research and technology advancement. The former generally focuses on studying phenomena happening in the real world, the latter improves tools that are at the basis of this research. From this perspective, information and communication technologies allow the implementation of ever faster tools for analyzing data generated by experiments. The aim of DemoGRAPE project is to study the interaction of the upper earth atmosphere and the GNSS (Global Navigation Satellite Systems) signals received at ground, in critical environments such as the polar regions. This paper describes the ICT infrastructure used to manage the software applications used to analyzed data collected during project experimental campaigns, taking into account the following constraints: (i) the intellectual property of the applications must be protected, (ii) the underlying infrastructure resembles a cloud-federation, (iii) data are over-sized, (iv) provide a unified vision of the available resources to the user (i.e., what are the available applications, and where experimental data reside). Leveraging on a lightweight virtualization system, we proposed a management system that copes with all these four constraints. A case study is used to show the process of deploying an application through the proposed system on a specific node where data of interest reside.

Satellite‐beacon Ionospheric‐scintillation Global Model of the upper Atmosphere (SIGMA) II: Inverse modeling with high‐latitude observations to deduce irregularity physics

Complex magnetosphere-ionosphere coupling mechanisms result in high-latitude irregularities that are difficult to characterize using only Global Navigation Satellite System (GNSS) scintillation measurements. However, GNSS observations combined with physical parameters derived from modeling can be used to study the physics of these irregularities. We have developed a full three-dimensional electromagnetic wave propagation model called “Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere” (SIGMA), to simulate GNSS scintillations. This model eliminates the most significant approximation made by the previous simulation approaches about the correlation length of the irregularity. Thus, for the first time, using SIGMA, we can accomplish scintillation simulations of significantly high fidelity. While the model is global, it is particularly applicable at high latitudes as it accounts for the complicated geometry of the magnetic field lines in these regions. Using SIGMA, we simulate the spatial and temporal variations in the GNSS signal phase and amplitude on the ground. In this paper, we present the model and results from a study to determine the sensitivity of the SIGMA outputs to different input parameters. We have deduced from our sensitivity study that the peak to peak (P2P) power gets most affected by the spectral index and line of sight direction, while the P2P phase and standard deviation of the phase (σφ) are more sensitive to the anisotropy of the irregularity. The sensitivity study of SIGMA narrows the parametric space to investigate when comparing the modeled results to the observations.

GNSS Based Services on Cloud Environment

The ionosphere is the single largest contributor to the GNSS (Global Navigation Satellite System) error budget and ionospheric scintillation (IS) in particular is one of its most harmful effects. The Ground Based Scintillation Climatology (GBSC) has been recently developed by INGV as a software tool to identify the main areas of the ionosphere in which IS is more likely to occur. Due to the high computational load required, GBSC is currently used only for scientific, offline, studies and not as a real time service. Recently, a collaboration was initiated between ISMB and INGV in order to identify which cloud service model (IaaS, PaaS or SaaS) is most suitable for implementing the GBSC technique within the cloud computing environment. The aims of this joined effort are twofold: i) to optimize the computational resources allocation strategy/plan for the GBSC service, ii) to fine tune the algorithm for dynamic and real time application, towards a service contributing to high precision professional applications for the GNSS-reliant business sectors. Preliminary result of the implementation of GBSC within the cloud environment will be shown.

Low latitude scintillations: A comparison of modeling and observations within the CIGALA project

Ionospheric scintillations can seriously jeopardize the reliability of the GNSS signals and consequently can cause significant error or outage on precise positioning applications. The threat is most acute at low latitudes where ionospheric irregularities are more likely to occur resulting in L-band signal scintillations. This paper describes the effort made to model the ionospheric scintillations over the Latin American region in the frame of the CIGALA project funded by the European GNSS Supervisory Authority within the 7th Framework Programme of the European Commission. Comparisons between the low-latitude model of scintillations and observations are here presented and discussed within the project perspectives.

Analysis of the Regional Ionosphere at Low Latitudes in Support of the Biomass ESA Mission

Biomass is a spaceborn polarimetric P-band (435 MHz) synthetic aperture radar (SAR) in a dawn–dusk low Earth orbit. Its principal objective is to measure biomass content and change in all the Earth’s forests. The ionosphere introduces the Faraday rotation on every pulse emitted by low-frequency SAR and scintillations when the pulse traverses a region of plasma irregularities, consequently impacting the quality of the imaging. Some of these effects are due to total electron content (TEC) and its gradients along the propagation path. Therefore, an accurate assessment of the ionospheric morphology and dynamics is necessary to properly understand the impact on image quality, especially in the equatorial and tropical regions. To this scope, we have conducted an in-depth investigation of the significant noise budget introduced by the two crests of the equatorial ionospheric anomaly (EIA) over Brazil and Southeast Asia. This paper is characterized by a novel approach to conceive a SAR-oriented ionospheric assessment, aimed at detecting and identifying spatial and temporal TEC gradients, including scintillation effects and traveling ionospheric disturbances, by means of Global Navigation Satellite Systems ground-based monitoring stations. The novelty of this approach resides in the customization of the information about the impact of the ionosphere on SAR imaging as derived by local dense networks of ground instruments operating during the passes of Biomass spacecraft. The results identify the EIA crests as the regions hosting the bulk of irregularities potentially causing degradation on SAR imaging. Interesting insights about the local characteristics of low-latitudes ionosphere are also highlighted.

Performance of ionospheric maps in support of long baseline GNSS kinematic positioning at low latitudes

Ionospheric scintillation occurs mainly at high and low latitude regions of the Earth and may impose serious degradation on GNSS (Global Navigation Satellite System) functionality. The Brazilian territory sits on one of the most affected areas of the globe, where the ionosphere behaves very unpredictably, with strong scintillation frequently occurring in the local postsunset hours. The correlation between scintillation occurrence and sharp variations in the ionospheric total electron content (TEC) in Brazil is demonstrated in Spogli et al. (2013). The compounded effect of these associated ionospheric disturbances on long baseline GNSS kinematic positioning is studied in this paper, in particular when ionospheric maps are used to aid the positioning solution. The experiments have been conducted using data from GNSS reference stations in Brazil. The use of a regional TEC map generated under the CALIBRA (Countering GNSS high-Accuracy applications Limitations due to Ionospheric disturbances in BRAzil) project, referred to as CALIBRA TEC map (CTM), was compared to the use of the Global Ionosphere Map (GIM), provided by the International GNSS Service (IGS). Results show that the use of the CTM greatly improves the kinematic positioning solution as compared with that using the GIM, especially under disturbed ionospheric conditions. Additionally, different hypotheses were tested regarding the precision of the TEC values obtained from ionospheric maps, and its effect on the long baseline kinematic solution evaluated. Finally, this study compares two interpolation methods for ionospheric maps, namely, the Inverse Distance Weight and the Natural Neighbor.

A Filtering Method Developed to Improve GNSS Receiver Data Quality in the CALIBRA Project

To study ionospheric scintillation on L-band radio signals, it is nowadays typical to acquire data with GNSS (Global Navigation Satellite System) receivers working at high frequency sampling rate (50-100 Hz) [1]. When dealing with such data, it is common to consider the contribution coming solely from observations at elevation angles, calculated from the receiver to the selected satellite, above an arbitrary threshold, typically 15-30°. Filtering out measure‐ ments made at low elevation angles helps keeping a high SNR (Signal to Noise Ratio) and eliminating non-ionospheric related effects, such as multipath [2].