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  • 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
  • CO2
  • Elsevier Science Limited  (5)
  • Blackwell Science Ltd  (3)
  • Ahmedabad, India  (1)
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  • 1
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    Translated origin spherical cap harmonic analysis (2008)
    Blackwell Science Ltd
    Details
    Publication Date: 2017-04-03
    Description: The method of spherical cap harmonic analysis (SCHA), due to Haines (1985) is appropriate for regional geomagnetic field modelling as it includes the required potential field constraints and, for a given number of model parameters, describes shorter wavelength features than a global spherical harmonic model. If the origin of the coordinate system is moved from the centre of the Earth towards the surface then the Earth's surface is no longer equidistant from the origin. At the Earth's surface the minimum wavelength described by a SCH model in the new coordinate system is smaller at the centre of the region than at the edge. This method of translated origin spherical cap harmonic analysis (TOSCA) has been applied to regional field modelling for Italy. The method is able to take advantage of the dense distribution of data at the centre of region and the model effectively smooths towards the periphery. The performance of the TOSCA model is discussed in relation to a model derived using conventional SCHA.
    Description: Published
    Description: 253-263
    Description: N/A or not JCR
    Description: reserved
    Keywords: ground and satellite data analysis ; regional field modelling ; spherical cap harmonic analysis ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Source ambiguity from an estimation of the scaling exponent of potential field power spectra (2008)
    Blackwell Science Ltd
    Details
    Publication Date: 2017-04-04
    Description: An analysis of the field scaling power spectrum yields useful information about the source distribution, but it is uncertain whether deterministic, random, fractal or mixed approaches have to be used for the interpretation. To this end, the scaling properties of potential field spectra are analysed for a number of different source models of geological interest. Besides the models of Naidu (purely random sources) and Spector and Grant (gross block statistical ensembles) we consider other types of density and magnetization distributions with spectral exponents in the fractal range, such as a single homogeneous body with a random white source distribution. Spectral slopes in the fractal range are obtained. We also study the effects of important natural sources, such as salt domes and sedimentary basins, representing them with simple Gaussians or combinations of Gaussian signals. The same spectral slopes as for gravity signals generated by 3-D fractal source distributions are found for them. Hence the power law decay of the field is not a characteristic only of fractal source models. If a 3-D fractal source distribution is assumed a priori, a way of verifying the goodness of the model is to examine the whitened field at source level. The probability that the whitened field derives from a random white population is estimated for synthetic and real anomalies by applying the usual statistical tests.
    Description: Published
    Description: 311-323
    Description: JCR Journal
    Description: reserved
    Keywords: fractals ; potential field ; spectral analysis ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Tectonic control over large-scale diffuse degassing in eastern Sicily (Italy) (2005)
    Blackwell Science Ltd
    Details
    Publication Date: 2017-04-04
    Description: Eastern Sicily (southern Italy) is characterised by the presence of many natural gas emissions (mofettes, mud volcanoes). These gases are mostly carbon dioxide and methane, with minor amounts of helium, hydrogen, carbon monoxide and hydrocarbons. In this study, the extent and orientation of soil gas anomalies (He and CO2) were investigated on a wide area (approximately 110 km2) located just SW of Mt. Etna. From a structural point of view, this area lays on a typical foredeep–foreland system that marks the boundary between the southern part of the Eurasian plate and the northern part of the African plate in the central Mediterranean. No tectonic structure was revealed in this area by surface geological surveys. Very high soil emissions were found, and their spatial pattern reveals the existence of some active faults all directed about N508E. This direction coincides with that of two major fault systems that cut eastern Sicily and are evident, respectively, NE and SW of the study area. Soil gas data suggest that these fault systems are the expression of a single continuous structural line which is probably responsible for the past and present magma uprise in eastern Sicily. Isotopic values of carbon of CO2 suggest a minor contribution of organic carbon. Moreover, in the highest degassing sites the isotopic values of He found in association with CO2 (He abundance¼11–70 p.p.m.; R/Ra between 6.0 and 6.2) suggest that both gases are mantle derived. The extent of the areas affected by high gas emissions and the amounts of deep CO2 emitted in the investigated area (several hundred tonnes per day) may provide additional supporting evidence of a mantle upwelling taking place beneath this region.
    Description: Gruppo Nazionale per la Vulcanologia Italy.
    Description: Published
    Description: 273–284
    Description: partially_open
    Keywords: CO2 ; diffuse degassing ; Sicily ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 597 bytes
    Format: 866788 bytes
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  • 4
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    Soil gases and SAR measurements reveal hidden faults on the sliding flank of Mt. Etna (Italy) (2012)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: From October 2008 to November 2009, soil CO2, radon and structural field surveys were performed on Mt. Etna, in order to acquire insights into active tectonic structures in a densely populated sector of the south-eastern flank of the volcano, which is involved in the flank dynamics, as highlighted by satellite data (InSAR). The studied area extends about 150 km2, in a sector of the volcano where InSAR results detected several lineaments that were not well-defined from previous geological surveys. In order to validate and better constrain these features with ground data evidences, soil CO2 and soil radon measurements were performed along transects roughly orthogonal to the newly detected faults, with measurement points spaced about 100 m. In each transect, the highest CO2 values were found very close to the lineaments evidenced by InSAR observations. Anomalous soil CO2 and radon values were also measured at old eruptive fractures. In some portions of the investigated area soil gas anomalies were rather broad over transects, probably suggesting a complex structural framework consisting of several parallel volcano-tectonic structures, instead of a single one. Soil gas measurements proved particularly useful in areas at higher altitude on Mt. Etna (i.e. above 900 m asl), where InSAR results are not very informative/ are fairly limited, and allowed recognizing the prolongation of some tectonic lineaments towards the summit of the volcano. At a lower altitude on the volcanic edifice, soil gas anomalies define the active structures indicated by InSAR results prominently, down to almost the coastline and through the northern periphery of the city of Catania. Coupling InSARwith soil gas prospectingmethods has thus proved to be a powerful tool in detecting hidden active structures that do not show significant field evidences.
    Description: This work was funded by the DPC-INGV project “Flank”
    Description: Published
    Description: 27-40
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: CO2 ; Radon ; InSAR ; Faults ; Etna ; Volcano-tectonics ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    The calculation of ionospheric absorption with modern computers (2014)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: New outcomes are proposed for ionospheric absorption starting from the Appleton-Hartree formula, in its complete form. The range of applicability is discussed for the approximate formulae, which are usually employed in the calculation of non-deviative absorption coefficient. These results were achieved by performing a more refined approximation that is valid under quasi-longitudinal (QL) propagation conditions. The more refined QL approximation and the usually employed non-deviative absorption are compared with that derived from a complete formulation. Their expressions, nothing complicated, can usefully be implemented in a software program running on modern computers. Moreover, the importance of considering Booker’s rule is highlighted. A radio link of ground range D = 1000 km was also simulated using ray tracing for a sample daytime ionosphere. Finally, some estimations of the integrated absorption for the radio link considered are provided for different frequencies.
    Description: Published
    Description: 1642-1650
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Description: open
    Keywords: Appleton-Hartree formula ; more refined quasi-longitudinal approximation ; usually employed non-deviative absorption ; Booker’s rule ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.01. Ion chemistry and composition ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Volcanic plume vent conditions retrieved from infrared images: A forward and inverse modeling approach (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2020-02-24
    Description: We present a coupled fluid-dynamic and electromagnetic model for volcanic ash plumes. In a forward approach, the model is able to simulate the plume dynamics from prescribed input flow conditions and generate the corresponding synthetic thermal infrared (TIR) image, allowing a comparison with field-based observations. An inversion procedure is then developed to retrieve vent conditions from TIR images, and to independently estimate the mass eruption rate. The adopted fluid-dynamic model is based on a one-dimensional, stationary description of a self-similar turbulent plume, for which an asymptotic analytical solution is obtained. The electromagnetic emission/absorption model is based on Schwarzschild's equation and on Mie's theory for disperse particles, and we assume that particles are coarser than the radiation wavelength (about 10 μm) and that scattering is negligible. In the inversion procedure, model parameter space is sampled to find the optimal set of input conditions which minimizes the difference between the experimental and the synthetic image. Application of the inversion procedure to an ash plume at Santiaguito (Santa Maria volcano, Guatemala) has allowed us to retrieve the main plume input parameters, namely mass flow rate, initial radius, velocity, temperature, gas mass ratio, entrainment coefficient and their related uncertainty. Moreover, by coupling with the electromagnetic model we have been able to obtain a reliable estimate of the equivalent Sauter diameter of the total particle size distribution. The presented method is general and, in principle, can be applied to the spatial distribution of particle concentration and temperature obtained by any fluid-dynamic model, either integral or multidimensional, stationary or time-dependent, single or multiphase. The method discussed here is fast and robust, thus indicating potential for applications to real-time estimation of ash mass flux and particle size distribution, which is crucial for model-based forecasts of the volcanic ash dispersal process.
    Description: Published
    Description: 129–147
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 4V. Vulcani e ambiente
    Description: 5V. Sorveglianza vulcanica ed emergenze
    Description: JCR Journal
    Description: restricted
    Keywords: Volcanic ash plume ; Volcanic ash plume ; Thermal camera ; Inversion ; Mass flow ; Particle size ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.04. Thermodynamics ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.01. Data processing ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    The COMPLEIK subroutine of the IONORT-ISP system for calculating the non-deviative absorption: A comparison with the ICEPAC formula (2014)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: The present paper proposes to discuss the ionospheric absorption, assuming a quasi-flat layered ionospheric medium, with small horizontal gradients. A recent complex eikonal model [Settimi et al., 2013b] is applied, useful to calculate the absorption due to the ionospheric D-layer, which can be approximately characterized by a linearized analytical profile of complex refractive index, covering a short range of heights between h1= 50 km and h2= 90 km. Moreover, Settimi et al. [2013c] have already compared the complex eikonal model for the D-layer with the analytical Chapman’s profile of ionospheric electron density; the corresponding absorption coefficient is more accurate than Rawer’s theory [1976] in the range of middle critical frequencies. Finally, in this paper, the simple complex eikonal equations, in quasi-longitudinal (QL) approximation, for calculating the non-deviative absorption coefficient due to the propagation across the D-layer are encoded into a so called COMPLEIK (COMPLex EIKonal) subroutine of the IONORT (IONOspheric Ray-Tracing) program [Azzarone et al., 2012]. The IONORT program, which simulates the three-dimensional (3-D) ray-tracing for high frequencies (HF) waves in the ionosphere, runs on the assimilative ISP (IRI-SIRMUP-P) discrete model over the Mediterranean area [Pezzopane et al., 2011]. As main outcome of the paper, the simple COMPLEIK algorithm is compared to the more elaborate semi-empirical ICEPAC formula [Stewart, undated], which refers to various phenomenological parameters such as the critical frequency of E-layer. COMPLEIK is reliable just like the ICEPAC, with the advantage of being implemented more directly. Indeed, the complex eikonal model depends just on some parameters of the electron density profile, which are numerically calculable, such as the maximum height.
    Description: Published
    Description: 201-218
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Description: partially_open
    Keywords: Ionospheric D-layer ; Quasi-Longitudinal propagation ; non-deviative absorption ; ICEPAC formula ; ISP-IONORT ; Complex Eikonal theory ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.01. Ion chemistry and composition ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous ; 05. General::05.07. Space and Planetary sciences::05.07.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Correction’s method of the electron density model in ionosphere by ray tracing techniques (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: When applying the ray tracing in ionospheric propagation, the electron density modelling is the main input of the algorithm, since phase refractive index strongly depends on it. Also the magnetic field and frequency collision modelling have their importance, the former as responsible for the azimuth angle deviation of the vertical plane containing the radio wave, the latter for the evaluation of the absorption of the wave. Anyway, the electron density distribution is strongly dominant when one wants to evaluate the group delay time characterizing the ionospheric propagation. From the group delay time, azimuth and elevation angles it is possible to determine the point of arrival of the radio wave when it reaches the Earth surface. Moreover, the procedure to establish the target (T) position is one of the essential steps in the Over The Horizon Radar (OTHR) techniques which require the correct knowledge of the electron density distribution. The group delay time generally gives rough information of the ground range, which depends on the exact path of the radio wave in the ionosphere. This paper focuses on the lead role that is played by the variation of the electron density grid into the ray tracing algorithm, which is correlated to the change of the electron content along the ionospheric ray path, for obtaining a ray tracing as much reliable as possible. In many cases of practical interest, the group delay time depends on the geometric length and the electron content of the ray path. The issue is faced theoretically, and a simple analytical relation, between the variation of the electron content along the path and the difference in time between the group delays, calculated and measured, both in the ionosphere and in the vacuum, is obtained and discussed. An example of how an oblique radio link can be improved by varying the electron density grid is also shown and discussed.
    Description: Published
    Description: 1630-1639
    Description: 2A. Fisica dell'alta atmosfera
    Description: 1IT. Reti di monitoraggio e Osservazioni
    Description: JCR Journal
    Description: partially_open
    Keywords: Ionospheric ray tracing ; Electron density model ; Ray path correction ; Electron content ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation ; 05. General::05.04. Instrumentation and techniques of general interest::05.04.99. General or miscellaneous ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous ; 05. General::05.07. Space and Planetary sciences::05.07.99. General or miscellaneous ; 05. General::05.07. Space and Planetary sciences::05.07.02. Space weather
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    IIOE-2 Cruise No.EP12-1, 15 April, 2017 - 03 May, 2017 Kochi, India - Goa, India. Dust induced Primary Productivity and N2 fixation experiments in the Arabian Sea. (2017)
    Physical Research Laboratory | Ahmedabad, India
    Details
    Publication Date: 2021-05-19
    Description: Oceans act as a major sink for anthropogenic CO2 through primary production. The Arabian Sea (area ~6.2 × 106 km2) covers only about 1% of the global ocean surface but contributes up to 5% of the global marine primary production, partly due to high influx of ‘new’ nitrogen via diazotrophic N2 fixation. Iron, whose main source in the ocean is atmospheric transport of dust, is an essential nutrient for sustaining N2 fixation. Despite being in the vicinity of the Thar desert on the east and the Arabia desert on the west, the Arabian Sea has been projected to be an HNLC (high nutrient low chlorophyll) region
    Description: Unpublished
    Keywords: IIOE-2 ; CO2 ; Primary production ; Sagar Sampada/FORV ; Nitrogen fixation
    Repository Name: AquaDocs
    Type: Report , Not Known
    Format: 6pp.
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