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http://hdl.handle.net/2122/99
Thu, 02 Apr 2015 03:08:20 GMT2015-04-02T03:08:20ZThe IONORT-ISP-WC system: inclusion of an electron collision frequency model for the D-layer
http://hdl.handle.net/2122/9417
Title: The IONORT-ISP-WC system: inclusion of an electron collision frequency model for the D-layer
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; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: The IONORT-ISP system (IONOspheric Ray-Tracing – IRI-SIRMUP-PROFILES) was recently developed and tested by comparing the measured oblique ionograms over the radio link between Rome (41.89ºN, 12.48ºE), Italy, and Chania (35.51ºN, 24.02ºE), Greece, with the IONORT-ISP simulated oblique ionograms (Settimi et al., 2013). The present paper describes an upgrade of the system to include: a) electron-neutral collision have been included by using a collision frequency model that consists of a double exponential profile; b) the ISP three dimensional (3-D) model of electron density profile grid has been extended down to the altitude of the D-layer; c) the resolution in latitude and longitude of the ISP 3-D model of electron density profile grid has been increased from 2°x2° to 1°x1°. Based on these updates, a new software tool called IONORT-ISP-WC (WC means with collisions) was developed, and a database of 33 IONORT-ISP-WC synthesized oblique ionograms calculated for single (1-hop paths) and multiple (3-hop paths) ionospheric reflections. The IONORT-ISP-WC simulated oblique ionograms were compared with the IONORT-IRI-WC synthesized oblique ionograms, generated by applying IONORT in conjunction with the International Reference Ionosphere (IRI) 3-D electron density grid, and the observed oblique ionograms over the aforementioned radio link. The results obtained show that (1) during daytime, for the lower ionospheric layers, the traces of the synthesized ionograms are cut away at low frequencies because of HF absorption; (2) during night-time, for the higher ionospheric layers, the traces of the simulated ionograms at low frequencies are not cut off (very little HF absorption); (3) the IONORT-ISP-WC MUF values are more accurate than the IONORT-IRI-WC MUF values.
Description: SPECIAL ISSUE: International Reference Ionosphere (IRI) and Global Navigation Satellite Systems (GNSS)Tue, 14 Apr 2015 22:00:00 GMThttp://hdl.handle.net/2122/94172015-04-14T22:00:00ZCorrection’s method of the electron density model in ionosphere by ray tracing techniques
http://hdl.handle.net/2122/9340
Title: Correction’s method of the electron density model in ionosphere by ray tracing techniques
Authors: 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
Abstract: 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.Sat, 14 Mar 2015 23:00:00 GMThttp://hdl.handle.net/2122/93402015-03-14T23:00:00ZAutomatic interpretation of oblique ionograms
http://hdl.handle.net/2122/9339
Title: Automatic interpretation of oblique ionograms
Authors: Ippolito, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Scotto, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francis, M.; IPS Radio & Space Services, Bureau of Meteorology, Level 15, Tower C, 300 Elizabeth Street, Sydney, Australia; Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cesaroni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: We present an algorithm for the identification of trace characteristics of oblique ionograms allowing determination of the Maximum Usable Frequency (MUF) for communication between the transmitter and receiver. The algorithm automatically detects and rejects poor quality ionograms. We performed an exploratory test of the algorithm using data from a campaign of oblique soundings between Rome, Italy (41.90 N, 12.48 E) and Chania, Greece (35.51 N, 24.01 E) and also between Kalkarindji, Australia (17.43 S, 130.81 E) and Culgoora, Australia (30.30 S, 149.55 E). The success of these tests demonstrates the applicability of the method to ionograms recorded by different ionosondes in various helio and geophysical conditions.Sat, 14 Mar 2015 23:00:00 GMThttp://hdl.handle.net/2122/93392015-03-14T23:00:00ZRay 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.Wed, 22 Oct 2014 22:00:00 GMThttp://hdl.handle.net/2122/91392014-10-22T22:00:00ZThe 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.Tue, 14 Oct 2014 22:00:00 GMThttp://hdl.handle.net/2122/91042014-10-14T22:00:00ZScientific 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.Tue, 05 Aug 2014 22:00:00 GMThttp://hdl.handle.net/2122/90712014-08-05T22:00:00ZDescription 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 %.Tue, 31 Dec 2013 23:00:00 GMThttp://hdl.handle.net/2122/89782013-12-31T23:00:00ZThe 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.Tue, 14 Jan 2014 23:00:00 GMThttp://hdl.handle.net/2122/88642014-01-14T23:00:00ZTesting 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.Tue, 04 Dec 2012 23:00:00 GMThttp://hdl.handle.net/2122/88572012-12-04T23:00:00ZRetrieval 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.Sat, 30 Nov 2013 23:00:00 GMThttp://hdl.handle.net/2122/88532013-11-30T23:00:00Z