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  • 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous  (19)
  • 04.08. Volcanology
  • Data analysis / ~ processing
  • INGV  (19)
  • American Geophysical Union
  • Inst. f. Geophys., Ruhr-Univ. Bochum
  • International Union of Crystallography (IUCr)
  • Wiley
  • 2005-2009  (19)
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  • 1
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    Comparison of ionospheric scintillation models with experimental data for satellite navigation applications (2006)
    INGV
    Details
    Publikationsdatum: 2021-05-17
    Beschreibung: A comparison between two of the most used scintillation models and experimental data is presented. The experimental data have been derived from a GPS scintillation monitor developed at Cornell University and placed in Tucuman (Argentina), under the peak of the anomaly. The models used (GISM and WBMOD) have been run for the geophysical conditions corresponding to the measurements. The comparison is done by subdividing the information on the basis of an ionospheric grid of 5°×5° surface square boxes. The comparison has been performed for several local times, from 18 LT until 04 LT. Here, only a few cases of particular interest are shown. The goal is to understand if the models are able to forecast actual scintillation morphology (from the satellite navigation systems point of view) and if they could be used to yield an estimate of scintillation effects on satellite navigation systems.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionospheric scintillations ; scintillation models ; GPS ; SBAS ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 2
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    The TID model for modulation of large scale electron density models (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: Various modern applications of empirical electron density models need realistic structures of the electron density distribution with smaller scales than the model background. Travelling Ionospheric Disturbances (TIDs) produce three dimensional and time dependent disturbances of the background ionization. We present a TID model suitable to «modulate» large scale electron density distributions by multiplication. A model TID takes into account the forward tilt of the disturbance wave front, a distinct vertical structure, a fan type horizontal radiation characteristic, geometric dilution and attenuation. More complicated radiation patterns can be constructed by means of superposition. The model TIDs originate from source regions which can be chosen arbitrarily. We show examples for TID modulations of the background model family developed at Trieste and Graz (NeQuick, COSTprof and NeUoG-plas).
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionosphere ; electron density models ; Travelling Ionospheric Disturbances ; TID model ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 3
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    The response of the ionosphere to faint and bright solar flares as deduced from global GPS network data (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: Results derived from analysing the ionosphere response to faint and bright solar flares are presented. The analysis used technology of a global detection of ionospheric effects from solar flares as developed by the authors, on the basis of phase measurements of the Total Electron Content (TEC) in the ionosphere using an international GPS network. The essence of the method is that use is made of appropriate filtering and a coherent processing of variations in the TEC which is determined from GPS data, simultaneously for the entire set of visible GPS satellites at all stations used in the analysis. This technique is useful for identifying the ionospheric response to faint solar flares (of X-ray class C) when the variation amplitude of the TEC response to separate line-on-sight to GPS satellite is comparable to the level of background fluctuations. The dependence of the TEC variation response amplitude on the bright flares location on the Sun is investigated
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionopshere ; Total Electron Content ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 4
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    Statistical properties of the deviations of f 0 F 2 from monthly medians (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: The deviations of hourly f 0 F 2 from monthly medians for 20 stations in Europe during the period 1958-1998 are studied. Spectral analysis is used to show that, both for original data (for each hour) and for the deviations from monthly medians, the deterministic components are the harmonics of 11 years (solar cycle), 1 year and its harmonics, 27 days and 12 h 50.49 m (2nd harmonic of lunar rotation period L 2 ) periodicities. Using histograms for one year samples, it is shown that the deviations from monthly medians are nearly zero mean (mean 〈 0.5) and approximately Gaussian (relative difference range between %10 to %20) and their standard deviations are larger for daylight hours (in the range 5-7). It is shown that the amplitude distribution of the positive and negative deviations is nearly symmetrical at night hours, but asymmetrical for day hours. The positive and negative deviations are then studied separately and it is observed that the positive deviations are nearly independent of R12 except for high latitudes, but negative deviations are modulated by R12 . The 90% confidence interval for negative deviations for each station and each hour is computed as a linear model in terms of R12. After correction for local time, it is shown that for all hours the confidence intervals increase with latitude but decrease above 60N. Long-term trend analysis showed that there is an increase in the amplitude of positive deviations from monthly means irrespective of the solar conditions. Using spectral analysis it is also shown that the seasonal dependency of negative deviations is more accentuated than the seasonal dependency of positive deviations especially at low latitudes. In certain stations, it is also observed that the 4th harmonic of 1 year corresponding to a periodicity of 3 months, which is missing in f 0 F 2 data, appears in the spectra of negative variations.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): deviations ; solar cycle ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 5
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    The effects of f0 F2 variability on TEC prediction accuracy (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: In this paper hourly daily F2-layer critical frequency data recorded at Rome and one minute daily TEC data recorded at Florence were used and the relevant variabiles were calculated. It was concluded that there was no clear evidence as to how they correlated. In order to obtain a measure of the f 0 F 2 and TEC variability, the normalised differences df0 F2 and d TEC from the relevant monthly median values were also considered. Since no clear evidence could be obtained as of how df0 F2 and d TEC correlate, a new parameter, the ?Ap /?R ratio was tried. ?Ap was taken as the difference between the maximum value of Ap measured at the relevant disturbance and that corresponding at the beginning of the disturbance. ?R corresponded to the two above mentioned values of Ap. This parameter was compared to the differences of the corresponding df0 F2 values called ?df and d TEC values called ?dT. In wintertime, when ?A p /? R was negative, for the vast majority of the occurrences either ?df or ?dT was negative; ?df and ?dT were never observed to be negative at the same time whereas they were both positive in fewer than 10% of the observations. When ?A p /?R was positive then either ?df or ?dT were negative. In summertime when ?A p /?R was negative both ?df and ?dT were negative. When ?A p /?R was positive, while a positive ?df corresponded almost always to a positive ?dT, a negative ?df would equiprobably indicate either a positive or a negative ?dT.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionopshere ; ionospheric modelling ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 6
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    Investigation of the relative bottomside/topside contribution to the total electron content estimates (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: High-resolution vertical electron density true height profiles from Athens Digisonde are used to calculate the electron content up to the peak of the F 2 layer (bottomside electron content) and also the topside electron content up to 1000 km, using the Huang-Reinisch method, to investigate the relative behavior of these two parameters during storm events. It was shown that the topside electron content represents roughly the 2/3 of the total electron content of the ionosphere and it is strongly affected by the geomagnetic activity, much more than the bottomside electron content. During daylight hours the values of the topside electron content exhibit intense fluctuations, while they become smoother in nature during events of night-time F 2 layer uplifting caused by the auroral activity. All these facts demonstrate that the Huang-Reinisch method provides a realistic tool for monitoring the variations of the ionospheric ionisation at a given location and it could be used in the frames of a world wide effort for the development of realistic models to accurately predict the electron content and to support effectively earth-space communications including navigation systems.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): bottom side electron content ; topside electron content ; ionispheric storm effect ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 7
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    Proposed terminology for the classification and parameters for the quantification of variability in ionosphere morphology (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: Much uncertainty currently exists in the use by different workers of the term variability in describing the results of statistical analyses applied to ionospheric measurement data sets and in their relationships with various existing or new ionospheric models. Often it is not clear whether data for different time periods or different geographical areas, and if so which, are being used to formulate results. Terms are presented in the Annex which it is suggested should be used, at least once in every publication addressing this topic, to describe unambiguously what is talked about. The background to the proposed terminology is discussed. Options for variability parameters are also addressed.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionosphere ; ionospheroc terminology ; space and time variation ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 8
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    Comparisons of experimental topside electron concentration profiles with IRI and NeQuick models (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: A critical part of the vertical ionospheric electron concentration profile is the region above its maximum (topside ionosphere) and many attempts have been made to model this region because of the limited experimental data available. Recently, many topside electron concentration profiles obtained with the Intercosmos-19 satellite became accessible through the Internet. The period analyzed corresponds to March 1979 - December 1980, a time interval of high solar activity. The present work describes the comparison of these profiles with the IRI and NeQuick model profiles obtained by driving the models with the values of the maximum electron concentration and its height given by the satellite.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionospheric electron ; comparison profiles ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 9
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    Ionospheric topside models compared with experimental electron density profiles (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: Recently an increasing number of topside electron density profiles has been made available to the scientific community on the Internet. These data are important for ionospheric modeling purposes, since the experimental information on the electron density above the ionosphere maximum of ionization is very scarce. The present work compares NeQuick and IRI models with the topside electron density profiles available in the databases of the ISIS2, IK19 and Cosmos 1809 satellites. Experimental electron content from the F2 peak up to satellite height and electron densities at fixed heights above the peak have been compared under a wide range of different conditions. The analysis performed points out the behavior of the models and the improvements needed to be assessed to have a better reproduction of the experimental results. NeQuick topside is a modified Epstein layer, with thickness parameter determined by an empirical relation. It appears that its performance is strongly affected by this parameter, indicating the need for improvements of its formulation. IRI topside is based on Booker's approach to consider two parts with constant height gradients. It appears that this formulation leads to an overestimation of the electron density in the upper part of the profiles, and overestimation of TEC.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): topside ionosphere ; electron density models ; topside soundings ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 10
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    An improved bottomside for the ionospheric electron density model NeQuick (2006)
    INGV
    Details
    Publikationsdatum: 2019-11-04
    Beschreibung: The ionospheric electron density model NeQuick is a «profiler» which uses the peaks of the E-layer, the F1-layer and the F2-layer as anchor points. In the version prepared for and submitted to the International Telecommunication Union (ITU) the model uses the ITU-R (CCIR) maps for foF2 and M(3000)F2 and adapted maps similar to the ITU-R ones for foE and foF1. Since users found problematic behaviour of NeQuick under conditions of strong differences of foE and foF2 map structures, the profiling was adapted by changing the properties of the Epstein layers used for this purpose. The new formulation avoids both strange horizontal structures of the geographic distribution of electron density in fixed heights and unrealistic peculiarities of the height profile which occasionally occurred with the old version of the model. Since the Epstein layer approach allows for 8 parameters only (3 layer amplitudes and 5 semi-thicknesses) the adaptation was no minor task but needed careful planning of suitable strategies.
    Beschreibung: Published
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): ionosphere ; electron density models ; profilers ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.03. Forecasts
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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