DSpace Collection:
http://hdl.handle.net/2122/99
2014-11-23T22:13:40ZRay theory formulation and ray tracing method. Application in ionospheric propagation
http://hdl.handle.net/2122/9139
Title: Ray theory formulation and ray tracing method. Application in ionospheric propagation
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, S.; Dipartimento di Fisica, Università “Sapienza”, p.le Aldo Moro 2, 00185 Roma, Italia
Abstract: This work will lead to ray theory and ray tracing formulation. To deal with this problem the theory of classical geometrical optics is presented, and applications to ionospheric propagation will be described. This provides useful theoretical basis for scientists involved in research on radio propagation in inhomogeneous anisotropic media, especially in a magneto-plasma. Application in high frequencies (HF) radio propagation, radio communication, over-the-horizon-radar (OTHR) coordinate registration and related homing techniques for direction finding of HF wave, all rely on ray tracing computational algorithm. In this theory the formulation of the canonical, or Hamiltonian, equations related to the ray, which allow calculating the wave direction of propagation in a continuous, inhomogeneous and anisotropic medium with minor gradient, will be dealt. At least six Hamilton’s equations will be written both in Cartesian and spherical coordinates in the simplest way. These will be achieved by introducing the refractive surface index equations and the ray surface equations in an appropriate free-dimensional space. By the combination of these equations even the Fermat’s principle will be derived to give more generality to the formulation of ray theory. It will be shown that the canonical equations are dependent on a constant quantity H and the Cartesian coordinates and components of wave vector along the ray path. These quantities respectively indicated as ri(τ), pi(τ) are dependent on the parameter τ, that must increase monotonically along the path. Effectively, the procedure described above is the ray tracing formulation. In ray tracing computational techniques, the most convenient Hamiltonian describing the medium can be adopted, and the simplest way to choose properly H will be discussed. Finally, a system of equations, which can be numerically solved, is generated.2014-10-22T22:00:00ZThe calculation of ionospheric absorption with modern computers
http://hdl.handle.net/2122/9104
Title: The calculation of ionospheric absorption with modern computers
Authors: Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: 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.2014-10-14T22:00:00ZScientific review on the ionospheric absorption and research prospects of a Complex Eikonal model for one-layer ionosphere
http://hdl.handle.net/2122/9071
Title: Scientific review on the ionospheric absorption and research prospects of a Complex Eikonal model for one-layer ionosphere
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Ippolito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cesaroni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: Thepresent paper conducts a scientific review on ionospheric absorption, extrapolating the research prospects of a complex eikonal
model for one-layer ionosphere. As regards the scientific review, here a quasi-longitudinal (QL) approximation for nondeviative
absorption is deduced which is more refined than the corresponding equation reported by Davies (1990). As regards the research
prospects, a complex eikonal model for one-layer ionosphere is analyzed in depth here, already discussed by Settimi et al. (2013). A
simple formula is deduced for a simplified problem. A flat, layered ionospheric medium is considered, without any horizontal
gradient. The authors prove that the QL nondeviative amplitude absorption according to the complex eikonal model is more
accurate than Rawer’s theory (1976) in the range of middle critical frequencies.2014-08-05T22:00:00ZDescription of ionospheric disturbances observed by Vertical Ionospheric Sounding at 3 MHz
http://hdl.handle.net/2122/8978
Title: Description of ionospheric disturbances observed by Vertical Ionospheric Sounding at 3 MHz
Authors: Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, S.; Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: High Frequency radio waves reflected by the ionosphere can provide a
relevant amount of information within the composite received signal.
The ionosphere is indeed a frequency dispersive, bi-refractive, absorbing
medium, in which multipath propagation occurs due to disturbance on a
varied time-spatial scale. On the time-spatial level of Small Scale Disturbances
(SSD) the ionosphere dynamics, detectable by Vertical Ionospheric
Sounding (VIS), is mainly dependent on wrinkled layers acting as
multi-reflectors. The present paper discusses different aspects of the effects
of multipath fading suffered by the wave along the propagation path and
potentially associated with SSD. To achieve these objectives, a VIS campaign
at a fixed frequency of 3.0 MHz was conducted at the ionospheric
observatory in Rome (Latitude 41.8 N; Longitude 12.5 E), by collecting a
series of measurements of the power variations in received echo signals
recorded between two consecutive ionograms whose sounding repetition
rate was set to 15 min. The obtained results show that: 1) the fading suffered
by the wave follows either a Rayleigh trend or a Nakagami-Rice trend, or
a mix of them, the mixed case being the most frequent (about 65 % of the
analysed cases); 2) the predominant periodicities characterizing the power
variation are less than 25 s; such values are compatible with the small
scale ionospheric disturbances; 3) for all the 24 hours of the day the ionospheric
reflector is pretty stable and for time intervals of 10-30 s the periods
of stability occur with a percentage of occurrence ranging between 55%
and 95 %; for time intervals of 190- 210 s the periods of stability occur instead
with a percentage of occurrence ranging between 5% and 54 %.2013-12-31T23:00:00ZThe COMPLEIK subroutine of the IONORT-ISP system for calculating the non-deviative absorption: A comparison with the ICEPAC formula
http://hdl.handle.net/2122/8864
Title: The COMPLEIK subroutine of the IONORT-ISP system for calculating the non-deviative absorption: A comparison with the ICEPAC formula
Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: 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.2014-01-14T23:00:00ZTesting the three-dimensional IRI-SIRMUP-P mapping of the ionosphere for disturbed periods
http://hdl.handle.net/2122/8857
Title: Testing the three-dimensional IRI-SIRMUP-P mapping of the ionosphere for disturbed periods
Authors: Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pignatelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cander, Lj. R.
Abstract: This paper describes the three-dimensional (3-D) electron density mapping of the ionosphere given as output by the assimilative IRI-SIRMUP-P (ISP) model for three different geomagnetic storms. Results of the 3-D model are shown by comparing the electron density profiles given by the model with the ones measured at two testing ionospheric stations: Roquetes (40.8 °N,0.5 °E), Spain, and San Vito (40.6°N,17.8 °E), Italy. The reference ionospheric stations from which the autoscaled foF2 and M(3000)F2 data as well as the real-time vertical electron density profiles are assimilated by the ISP model are those of El Arenosillo (37.1 °N,353.3° E), Spain, Rome (41.8 °N,12.5 °E), and Gibilmanna (37.9° N,14.0 °E), Italy. Overall, the representation of the ionosphere made by the ISP model is better
than the climatological representation made by only the IRI-URSI and the IRI-CCIR models. However, there are few cases for which the assimilation of the autoscaled data from the reference stations causes either a strong underestimation or a strong overestimation of the real conditions of the ionosphere, which is in these cases better represented by only the IRI-URSI model. This ISP misrepresentation is mainly due to the fact that the reference ionospheric stations covering the region mapped by the model turn out to be few, especially for disturbed periods when the ionosphere is very variable both in time and in space and hence a larger number of stations would be required. The inclusion of new additional reference ionospheric stations could surely smooth out this concern.2012-12-04T23:00:00ZRetrieval of thermospheric parameters from routinely observed F2-layer Ne(h) proﬁles at the geomagnetic equator
http://hdl.handle.net/2122/8853
Title: Retrieval of thermospheric parameters from routinely observed F2-layer Ne(h) proﬁles at the geomagnetic equator
Authors: Mikhailov, A.; Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Troitsk, Moscow Region 142190, Russia; Belehaki, A.; Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Metaxa and Vas. Pavlou, Palaia Penteli, 15236 Greece; Perrone, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Tsagouri, I.; Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Metaxa and Vas. Pavlou, Palaia Penteli, 15236 Greece
Abstract: A principal possibility to retrieve basic thermospheric parameters (neutral temperature Tex, atomic [O] and molecular [O2] oxygen as well as molecular nitrogen [N2] concentrations) from the observed daytime electron density profiles Ne(h) in the equatorial F2-region is demonstrated for the first time. The reduction of a 2D continuity equation for electron concentration in the low-latitude F2-region at the geomagnetic equator (I = 0) results in a simple 1D equation which can be efficiently solved. The method was tested using Jicamarca Incoherent Scatter Radar (ISR) and Digisonde Ne(h) profiles for the periods when CHAMP and GRACE neutral gas density observations are available in the vicinity of the Jicamarca Observatory. The retrieved from ISR Ne(h) neutral gas densities were shown to be close to the observed ones (MRD < 10%) being within the announced absolute uncertainty (10–15%) of the neutral gas density observations and more successful than the predictions of the empirical models JB-2008 (MRD = 32%) and MSISE-00 (MRD = 27%) for the analyzed cases. The implementation of the method with Jicamarca Digisonde Ne(h) profiles has also shown acceptable results especially for solar minimum conditions (MRD ~ 12%) and higher prediction accuracy than modern empirical models provide. This finding seems to open a way for the practical exploitation of the method for thermospheric monitoring purposes.2013-11-30T23:00:00ZSolar activity impact on the Earth’s upper atmosphere
http://hdl.handle.net/2122/8851
Title: Solar activity impact on the Earth’s upper atmosphere
Authors: Kutiev, I.; National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences, 1113 Soﬁa, Bulgaria; Tsagouri, I.; Institute for Space Applications and Remote Sensing, National Observatory of Athens, 15236 Mount Penteli, Greece; Perrone, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pancheva, D.; National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences, 1113 Soﬁa, Bulgaria; Mukhtarov, P.; National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences, 1113 Soﬁa, Bulgaria; Mikhailov, A.; Institute of Terrestrial Magnetism, Ionosphere, and Radio Propagation, Russian Academy of Sciences, 142190 Troitsk, Moskovskaya obl., Russia 5 Institute of Atmospheric Physics ASCR, 14131 Prague, Czech Republic 6 Institute of Communications and Navigation, German Aerospace Center, 51147 Cologne, Germany 7 Ebro Observatory, University Ramon Llull, CSIC, E-43520 Roquetes, Spain 8 Dipartimento di Fisica, Universita` degli Studi di Roma, 00185 Rome, Italy 9 Atmospheric Sounding Station; Lastovicka, J.; Institute of Atmospheric Physics ASCR, 14131 Prague, Czech Republic; Jakowski, N.; Institute of Communications and Navigation, German Aerospace Center, 51147 Cologne, Germany; Buresova, D.; Institute of Atmospheric Physics ASCR, 14131 Prague, Czech Republic; Blanch, E.; Ebro Observatory, University Ramon Llull, CSIC, E-43520 Roquetes, Spain; Andonov, B.; National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences, 1113 Soﬁa, Bulgaria; Altadill, D.; Ebro Observatory, University Ramon Llull, CSIC, E-43520 Roquetes, Spain; Magdaleno, S.; Atmospheric Sounding Station ‘‘El Arenosillo’’, INTA, Huelva, Spain; Parisi, M.; Dipartimento di Fisica, Universita` degli Studi di Roma, 00185 Rome, Italy; Torta, J. M.; Ebro Observatory, University Ramon Llull, CSIC, E-43520 Roquetes, Spain
Abstract: The paper describes results of the studies devoted to the solar activity impact on the Earth’s upper atmosphere and ionosphere,
conducted within the frame of COST ES0803 Action.
Aim: The aim of the paper is to represent results coming from different research groups in a uniﬁed form, aligning their speciﬁc topics into the general context of the subject.
Methods: The methods used in the paper are based on data-driven analysis. Speciﬁc databases are used for spectrum analysis,
empirical modeling, electron density proﬁle reconstruction, and forecasting techniques.
Results: Results are grouped in three sections: Medium- and long-term ionospheric response to the changes in solar and geomag-
netic activity, storm-time ionospheric response to the solar and geomagnetic forcing, and modeling and forecasting techniques.
Section 1 contains ﬁve subsections with results on 27-day response of low-latitude ionosphere to solar extreme-ultraviolet (EUV)
radiation, response to the recurrent geomagnetic storms, long-term trends in the upper atmosphere, latitudinal dependence of total electron content on EUV changes, and statistical analysis of ionospheric behavior during prolonged period of solar activity.
Section 2 contains a study of ionospheric variations induced by recurrent CIR-driven storm, a case-study of polar cap absorption
due to an intense CME, and a statistical study of geographic distribution of so-called E-layer dominated ionosphere.
Section 3 comprises empirical models for describing and forecasting TEC, the F-layer critical frequency foF2, and the height of
maximum plasma density. A study evaluates the usefulness of effective sunspot number in specifying the ionosphere state. An
original method is presented, which retrieves the basic thermospheric parameters from ionospheric sounding data.2013-11-30T23:00:00ZMonitoraggio sismico del territorio nazionale: stato dell'arte e sviluppo delle reti di monitoraggio sismico
http://hdl.handle.net/2122/8813
Title: Monitoraggio sismico del territorio nazionale: stato dell'arte e sviluppo delle reti di monitoraggio sismico
Authors: Sergio, Guardato; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia
Abstract: Il sistema CUMAS (Cabled Underwater Module
for Acquisition of Seismological data) è un
prodotto tecnologico-scientifico complesso nato
con il Progetto V4 [Iannaccone et al., 2008] allo
scopo di monitorare l’area vulcanica dei Campi
Flegrei (fenomeno del bradisismo).
Si tratta di un modulo sottomarino cablato e
connesso a una boa galleggiante (meda elastica). Il
sistema è in grado di acquisire e trasmettere alla
sala di monitoraggio dell’OV, in continuo e in
tempo reale, sia i segnali sismologici sia quelli di
interesse geofisico ed oceanografico (maree,
correnti marine, segnali acustici subacquei,
parametri funzionali di varia natura).
Il sistema è in grado di ricevere comandi da remoto
per variare diversi parametri di acquisizione e di
monitorare un cospicuo numero di variabili di
funzionamento.
Il sistema si avvale del supporto di una boa
galleggiante attrezzata. La boa è installata a largo
del golfo di Pozzuoli (Napoli) a circa 3 km dalla
costa. Il modulo sottomarino, collegato via cavo
alla parte fuori acqua della boa, è installato sul
fondale marino a una profondità di circa 100 metri.2010-12-31T23:00:00ZMeasuring GNSS ionospheric total electron content at Concordia, and application to L-band radiometers
http://hdl.handle.net/2122/8734
Title: Measuring GNSS ionospheric total electron content at Concordia, and application to L-band radiometers
Authors: Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Macelloni, G.; Istituto di Fisica Applicata 'Nello Carrara' (IFAC-CNR), Sesto Fiorentino (Florence), Italy; Spogli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Brogioni, M.; Istituto di Fisica Applicata 'Nello Carrara' (IFAC-CNR), Sesto Fiorentino (Florence), Italy; Marinaro, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Mitchell, C. N.; University of Bath, Electronic and Electrical Engineering, Bath, United Kingdom
Abstract: In the framework of the project BIS - Bipolar Ionospheric Scintillation and Total Electron Content Monitoring, the ISACCO-DMC0 and ISACCO-DMC1 permanent monitoring stations were installed in 2008.
The principal scope of the stations is to measure the ionospheric total electron content (TEC) and to monitor the ionospheric scintillations, using high-sampling-frequency global positioning system (GPS) ionospheric scintillation and TEC monitor (GISTM) receivers. The disturbances that
the ionosphere can induce on the electromagnetic signals emitted by the
Global Navigation Satellite System constellations are due to the presence
of electron density anomalies in the ionosphere, which are particularly frequent
at high latitudes, where the upper atmosphere is highly sensitive to
perturbations coming from outer space. With the development of present and future low-frequency space-borne microwave missions (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active
Passive missions), there is an increasing need to estimate the effects of the ionosphere on the propagation of electromagnetic waves that affects
satellite measurements. As an example, how the TEC data collected at Concordia station are useful for the calibration of the European Space Agency SMOS data within the framework of an experiment promoted by the European Space Agency (known as DOMEX) will be discussed.
The present report shows the ability of the GISTM station to monitor ionospheric scintillation and TEC, which indicates that only the use of continuous GPS measurements can provide accurate information on TEC
variability, which is necessary for continuous calibration of satellite data.2012-12-31T23:00:00Z