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  • Articles  (4)
  • 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques  (2)
  • magnetotelluric  (2)
  • 1
    Publication Date: 2017-04-04
    Description: New systematic oblique ionospheric radio sounding measurements over Central Europe, concerning the radio links between Inskip (UK, 53.51N, 2.51W) and Rome (Italy, 41.81N, 12.51E) and between Inskip and Chania (Greece, 35.71N, 24.01E), have been performed since November 2003. Different long-term (i.e. monthly median) ionospheric predictions and nowcasting techniques have been applied and compared with the oblique-incidence radio sounding measurements. The MUF (basic maximum usable frequency) measurements observed during the early part of the experiment have been used to compare the performances of different methods. The preliminary analysis has shown good performances for the long-term prediction models, in particular in winter months for ICEPAC (ionospheric communications enhanced profile analysis and circuit) and in equinox/summer months for ASAPS (advanced stand-alone prediction system) and SIRM&LKW (simplified ionospheric regional model & lockwood). The nowcasting methods SIRMUP&LKW (SIRM updating method & lockwood) and ISWIRM (instantaneous space weighted ionospheric regional model) reveal good results for moderate and disturbed geomagnetic conditions when compared with the long-term prediction methods.
    Description: Published
    Description: 854-865
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: reserved
    Keywords: Ionosphere ; Monthly median models ; Nowcasting models ; Oblique radio sounding ; 01. Atmosphere::01.02. Ionosphere::01.02.03. Forecasts ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: The three-dimensional (3-D) electron density representation of the ionosphere computed by the assimilative IRI-SIRMUP-P (ISP) model was tested using IONORT (IONOspheric Ray-Tracing), a software application for calculating a 3-D ray-tracing for high frequency (HF) waves in the ionospheric medium. A radio link was established between Rome (41.8°N, 12.5°E) in Italy, and Chania (35.7°N, 24.0°E) in Greece, within the ISP validity area, and for which oblique soundings are conducted. The ionospheric reference stations, from which the autoscaled foF2 and M(3000)F2 data and real-time vertical electron density profiles were assimilated by the ISP model, were Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E) in Italy, and Athens (38.0°N, 23.5°E) in Greece. IONORT was used, in conjunction with the ISP and the International Reference Ionosphere (IRI) 3-D electron density grids, to synthesize oblique ionograms. The comparison between synthesized and measured oblique ionograms, both in terms of the ionogram shape and the maximum usable frequency characterizing the radio path, demonstrates both that the ISP model can more accurately represent real conditions in the ionosphere than the IRI, and that the ray-tracing results computed by IONORT are reasonably reliable.
    Description: Published
    Description: 167–179
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: 5.4. Banche dati di geomagnetismo, aeronomia, clima e ambiente
    Description: JCR Journal
    Description: partially_open
    Keywords: Electron Density ; Ray-Tracing ; Oblique Ionogram ; IRI ; Assimilative Modelling ; 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::05.01.01. Data processing ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2019-11-04
    Description: The reliable detection and identification of electrotelluric anomalies that could be considered as precursory phenomena of earthquakes become fundamental aspects of earthquake prediction research. Special arrangements, in local and/or regional scale, of the geoelectric structure beneath the measuring point, may act as natural real-time "filters" on the ULF electrotelluric data improving considerably the signal to "magnetotelluric-noise" ratio of anomalies originated by probably non-magnetotelluric sources. Linear polarization, i.e. local channelling of the electric field on the surface is expected in cases where 3D-local inhomogeneities, producing strong shear distortion, are present in the vicinity of the monitoring site and/or when a 2D-regional geoelectrical setting exhibits high anisotropy. By assuming different generation mechanisms and modes of propagation for the electrotelluric anomalies that could be considered earthquake precursory phenomena, a rotationally originated residual electrotelluric field results, eliminating background magnetotelluric-noise and revealing "hidden" transient variations that could be associated to earthquakes. The suggested method is applicable in real-time data collection, thus simplifies and accelerates the tedious task of identification of suspicious signals. As an indicative example, the case of Ioannina (located in Northwestern Greece) is presented. The local polarization of the electrotelluric field varies dramatically even at neighboring points although the regional geoelectric strike direction does not change.+
    Description: JCR Journal
    Description: open
    Keywords: Electrotelluric ; Greece ; magnetotelluric ; Mohr circle ; noise reduction ; seismic precursor ; tensor decomposition ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 4990659 bytes
    Format: application/pdf
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  • 4
    Publication Date: 2019-11-04
    Description: A magnetotelluric (MT) profile comprising eight measuring sites was conducted in the Mygdonia basin, a European Seismological Test Site. The MT-stations were deployed in a direction almost perpendicular to the major axis of the sedimentary basin to cover the area between the Lagada and Volvi lakes. The earth beneath the measuring points was considered to consist of a 2D-regional basement coupled with local, near surface, 3D-inhomogeneities. Impedance tensor decomposition analysis in conjunction with the magnetotelluric study of Mohr circles was implemented in the MT-data. From the electric field polarization diagrams and the interpretation of the Mohr circles results it is inferred that the local structure at all the sites polarizes the electric field in comparable directions ranging from N60°E to N80°E, except for the cases of the two stations located at the northern and southern borders of the basin, where the boundary conditions produce a deviation. Furthermore, the deeper structure seems to be two-dimensional. The strike-direction of the 2D-basement was found to be ~ N70°E. Although the regional geological strike in the area is NW-SE, the regional geoelectric strike is more compatible with the orientation of the faults in the area.
    Description: Published
    Description: JCR Journal
    Description: open
    Keywords: magnetotelluric ; tensor decomposition ; Mohr Cycles ; Mygdonia Basin, Greece ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 426055 bytes
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