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Settimi, Alessandro
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- PublicationRestrictedSOLENOIDALITY OF A MAGNETIC INDUCTION FIELD AND CONSERVATION OF TOTAL MOMENTUM(INTERSCIENZE Srl, 2012-05-02)
; ; ;Severini, S.; Centro Interforze Studi per le Applicazioni Militari (CISAM), Via della Bigattiera lato monte 10, 56122 San Piero a Grado, Pisa, Italy ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ;Amoroso, Angelo; INTERSCIENZE Srl, Via Felice Casati 7/9, 20124 Milan, ItalyThe following scientific essay proposes to discuss the physical aspects of a system consisting of some non-relativistic massive charged particles, that are the sources in motion of an electromagnetic field (e.m.) propagating through the space, filled by a linear, homogeneous, and isotropic material medium. The physical link between the conservation of total momentum and the solenoidality of a magnetic induction field is investigated. After a careful review of all the more widely sustained didactic justifications for the solenoidality of magnetic induction, some properties of the Maxwell e.m. stress tensor are defined according to Minkowski. This study presents a new framework wherein the necessary condition for the free-divergence of magnetic induction in the entire space, here named as solenoidality condition, derives directly from the total momentum conservation of the system, i.e. sources plus field.108 30 - PublicationOpen AccessReal Time 3D Ionospheric Modelling with Ray Tracing Application over Mediterranean Area(2011-08-13)
; ; ; ;Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; This poster deals with some practical examples of instantaneous 3D modelling of regional ionosphere, based on ionosondes data from the Istituto Nazionale di Geofisica e Vulcanologia, INGV. Characteristic anchor points have been chosen for each ionospheric region. These points are joint by an adaptive ionospheric profiler derived from the one used in Autoscala. For the F2 region the anchor point is given by the real height hmF2 of the layer and its critical frequency foF2. These values are obtained basing on the observed heights (hmF2ROME[OBS] and hmF2GIBILMANNA[OBS]) and critical frequencies (foF2ROME[OBS] and foF2GIBILMANNA[OBS]) of the F2 layer, which are compared with the corresponding monthly median given by CCIR maps using Shimazaki’s formulation. The differences dhmF2ROME = hmF2ROME[OBS] - hmF2ROME[CCIR] dhmF2GIBILMANNA = hmF2 GIBILMANNA [OBS] - hmF2 GIBILMANNA [CCIR] are thus computed and used in Kriging method to update the values given by CCIR maps. For the F1 region the critical frequency is derived form a solar zenith angle dependent model adjusted to match the values of foF1 measured in Rome and Gibilmanna. For the E region the height is set to 110 km, while the critical frequency is estimated by a standard solar zenith angle and solar activity dependent model. The model produces as an output a 3D matrix which can be profitably used as an input for a Matlab/Fortran based ray tracing program recently developed at INGV.210 406 - PublicationRestrictedScientific review on the Complex Eikonal, and research perspectives for the Ionospheric Ray-tracing and Absorption(2013-03-20)
; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; The present paper conducts a scientific review on the complex eikonal, extrapolating the research perspectives on the ionospheric ray-tracing and absorption. As regards the scientific review, the eikonal equation is expressed, and some complex-valued solutions are defined corresponding to complex rays and caustics. Moreover, the geometrical optics is compared to the beam tracing method, introducing the limit of the quasi-isotropic and paraxial complex optics approximations. Finally, the quasi-optical beam tracing is defined as the complex eikonal method applied to ray-tracing, discussing the beam propagation in a cold magnetized plasma. As regards the research perspectives, this paper proposes to address the following scientific problem: in absence of electromagnetic (e.m.) sources, consider a material medium which is time invariant, linear, optically isotropic, generally dispersive in frequency and inhomogeneous in space, with the additional condition that the refractive index is assumed varying even strongly in space. The paper continues the topics discussed by Bianchi et al. [2009], proposing a novelty with respect to the other referenced bibliography: indeed, the Joule’s effect is assumed non negligible, so the medium is dissipative, and its electrical conductivity is not identically zero. In mathematical terms, the refractive index belongs to the field of complex numbers. The dissipation plays a significant role, and even the eikonal function belongs to the complex numbers field. Under these conditions, for the first time to the best of our knowledge, suitable generalized complex eikonal and transport equations are derived, never discussed in literature. Moreover, in order to solve the ionospheric ray-tracing and absorption problems, we hint a perspective viewpoint. The complex eikonal equations are derived assuming the medium as optically isotropic. However, in agreement with the quasi isotropic approximation of geometrical optics, these equations can be referred to the Appleton-Hartree’s refractive index for an ionospheric magneto-plasma, which becomes only weakly anisotropic in the presence of Earth’s magnetic induction field. Finally, a simple formula is deduced for a simplified problem. Consider a flat layering ionospheric medium, so without any horizontal gradient. The paper proposes a new formula, useful to calculate the amplitude absorption due to the ionospheric D-layer, which can be approximately modelled by a linearized complex refractive index, because covering a short range of heights, between h1= 50 km and h2= 80 km about.1687 363 - PublicationOpen AccessTesting the IONORT-ISP system: A comparison between synthesized and measured oblique ionograms(2013-05-03)
; ; ; ; ; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pietrella, M.; 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 ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Makris, J.; Technological Educational Institute of Crete, P.O. Box 1939 Chania, Crete, Greece; ; ; ; ; ; 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.20487 512 - PublicationOpen AccessFourier Domain Analysis performances of a RESPER probe(2010-09-28)
; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, ItaliaThis report proposes to discuss the Fourier domain analysis performances of a RESPER probe. A uniform ADC, which is characterized by a sensible phase inaccuracy depending on frequency, is connected to a Fast Fourier Transform (FFT) processor, that is especially affected by a round-off amplitude noise linked to both the FFT register length and samples number. If the register length is equal to 32 bits, then the round-off noise is entirely negligible, else, once bits are reduced to 16, a technique of compensation must occur. In fact, oversampling can be employed within a short time window, reaching a compromise between the needs of limiting the phase inaccuracy due to ADC and not raising too much the number of averaged FFT values sufficient to bound the round-off. Finally, the appendix presents an outline of somewhat lengthy demonstrations needed to calculate the amplitude and especially phase inaccuracies due to the round-off noise of FFT processors.162 131 - PublicationRestrictedCoherent control of stimulated emission inside one dimensional photonic crystals: strong coupling regime(2009-06-16)
; ; ; ; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Severini, S.; Centro Interforze Studi Applicazioni Militari (CISAM), Via della Bigattiera 10, 56122 San Piero a Grado, Pisa, Italy ;Sibilia, C.; Dipartimento di Energetica, Universit`a “La Sapienza” di Roma, via Scarpa 16, 00161 Roma, Italy ;Bertolotti, M.; Dipartimento di Energetica, Universit`a “La Sapienza” di Roma, via Scarpa 16, 00161 Roma, Italy ;Napoli, A.; Dipartimento di Scienze Fisiche ed Astronomiche, Universit`a di Palermo, via Archirafi 36, 90123 Palermo, Italy ;Messina, A.; Dipartimento di Scienze Fisiche ed Astronomiche, Universit`a di Palermo, via Archirafi 36, 90123 Palermo, Italy; ; ; ; ; The present paper discusses the stimulated emission, in strong coupling regime, of an atom embedded inside a one dimensional (1D) Photonic Band Gap (PBG) cavity which is pumped by two counter-propagating laser beams. Quantum electrodynamics is applied to model the atom-field interaction, by considering the atom as a two level system, the e.m. field as a superposition of normal modes, the coupling in dipole approximation, and the equations of motion in Wigner-Weisskopf and rotating wave approximations. In addition, the Quasi Normal Mode (QNM) approach for an open cavity is adopted, interpreting the local density of states (LDOS) as the local density of probability to excite one QNM of the cavity; and therefore rendering this LDOS dependent on the phase difference of the two laser beams. In this paper we demonstrate that the strong coupling regime occurs at high values of the LDOS. In accordance with the results of the literature, the emission probability of the atom decays with an oscillatory behaviour, so that the atomic emission spectrum exhibits two peaks (Rabi splitting). The novelty of this work is that the phase difference of the two laser beams can produce a coherent control of both the oscillations for the atomic emission probability and, as a consequence, of the Rabi splitting in the emission spectrum. Possible criteria to design active delay lines are finally discussed.350 25 - PublicationOpen AccessTeoria della propagazione radio nei mezzi disomogenei (Metodo dell’iconale)(2009-10)
; ; ; ;Bianchi, S.; Università Sapienza (Dipartimento di Fisica) ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; L'Istituto Nazionale di Geofisica e Vulcanologia si è occupato sin dalla sua fondazione della previsione delle condizioni in cui può aver luogo un radio collegamento che faccia uso della propagazione per onda ionosferica. Negli ultimi tempi ha assunto importanza anche il prevedere con precisione la traiettoria percorsa da un’onda radio che si propaga nell’atmosfera, in particolare nella ionosfera, che si può considerare, in prima approssimazione, come un mezzo non omogeneo, caratterizzato da un indice di rifrazione variabile lentamente nel tempo. Questo lavoro descrive le basi teoriche per lo studio di una traiettoria; esse fanno uso essenzialmente dei metodi dell’ottica geometrica. Tali basi teoriche trovano applicazione in metodi numerici di calcolo delle traiettorie, come citato in bibliografia [Bianchi, 2009].247 660 - PublicationOpen AccessIONORT: A Windows software tool to calculate the HF ray tracing in the ionosphere(UNIPRESS Casa Editrice e libreria Online Padova, 2012-05-30)
; ; ; ; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Azzarone, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ; ; ; ;Monorchio, A.; Universita` di Pisa via Diotisalvi 2 -- 56126 PISAThis proceeding describes an applicative software tool, named IONORT (IONOspheric Ray Tracing), for calculating a three-dimensional ray tracing of high frequency waves in the ionospheric medium. This tool runs under Windows operating systems and its friendly graphical user interface facilitates both the numerical data input/output and the two/three-dimensional visualization of the ray path. In order to calculate the coordinates of the ray and the three components of the wave vector along the path as dependent variables, the core of the program solves a system of six first order differential equations, the group path being the independent variable of integration. IONORT uses a three-dimensional electron density specification of the ionosphere, as well as geomagnetic field and neutral particles-electrons collision frequency models having validity in the area of interest.20372 8727 - PublicationOpen AccessScientific review on the ionospheric absorption and research prospects of a Complex Eikonal model for one-layer ionosphere(2014-08-06)
; ; ; ; ;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; ; ; 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.558 240 - PublicationOpen AccessCorrection’s method of the electron density model in ionosphere by ray tracing techniques(2015-03-15)
; ; ; ; ; ; ;Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bianchi, S.; Università Sapienza, Dipartimento di Fisica, p.le Aldo Moro 2, I-00185 Rome, Italy ;Baskaradas, J. A.; School of Electrical & Electronics Engineering, Shanmugha Arts, Science, Technology & Research Academy (SASTRA) University, Tirumalaisamudram, Thanjavur, 613 401 Tamilnadu, India; ; ; ; ; 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.776 424