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http://hdl.handle.net/2122/94
2015-01-27T14:24:18ZOn the possible use of radio occultation middle latitude electron density profiles to retrieve thermospheric parameters
http://hdl.handle.net/2122/9210
Title: On the possible use of radio occultation middle latitude electron density profiles to retrieve thermospheric parameters
Authors: Mikhailov, A.; Izmiran, Russia; Beleaki, A.; NOA, 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.; NOA, Greece
Abstract: This paper investigates possible use of middle latitude daytime COSMIC and CHAMP ionospheric radio occultation (IRO)
electron density profiles (EDPs) to retrieve thermospheric parameters, based on the Mikhailov et al. (2012) method. The aim of
this investigation is to assess the applicability of this type of observations for the routine implementation of the method. According
to the results extracted from the analysis presented here, about half of COSMIC IRO EDP observed under solar minimum
(2007–2008) conditions gave neutral gas density with an inaccuracy close to the declared absolute inaccuracy ±(10–15)% of
CHAMP observations, with the results being better than the empirical models JB-2008 and MSISE-00 provide. For the other half
of IRO EDP, either the solution provided by the method had to be rejected due to insufficient accuracy or no solution could be
obtained. For these cases, the parameters foF2 and hmF2 extracted from the corresponding IRO profiles have been found to be
inconsistent with the classic mid-latitude daytime F2-layer formalism that the method relies on, and they are incompatible with
the general trend provided by the IRI model. For solar maximum conditions (2002) the method was tested with IRO EDP from
CHAMP and it is indicated that its performance is quite stable in the sense that a solution could be obtained for all the cases
analyzed here. However available CHAMP EDP are confined by ~ 400 km in altitude and this might be the reason for the
20% bias of the retrieved densities toward larger values in respect to the observed densities. IRO observations up to 600 km under
solar maximum are required to confirm the exact performance of the method.2014-02-27T23:00:00ZComment on “The winter anomaly in the middlelatitude F region during the solar minimum period observed by the Constellation Observing System for Meteorology, Ionosphere, and Climate” by W. K. Lee, H. Kil, Y.-S. Kwak, Q. Wu, S. Cho, and J. U. Park
http://hdl.handle.net/2122/9195
Title: Comment on “The winter anomaly in the middlelatitude F region during the solar minimum period observed by the Constellation Observing System for Meteorology, Ionosphere, and Climate” by W. K. Lee, H. Kil, Y.-S. Kwak, Q. Wu, S. Cho, and J. U. Park
Authors: Mikhailov, A.; Perrone, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: Seasonal or winter anomaly in the F2 layer has been known since the beginning of regular ionospheric
observations [e.g., Berkner and Wells, 1938, and references therein], and one may be sure that such a
fundamental feature of this phenomenon as its height extent has been analyzed. However, Lee et al. [2011]
using radio occultation Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)
Ne(h) observations have decided to reconsider this problem starting from the very beginning without any
analyses of previous investigations and comparisons to earlier obtained results as if ionospheric F2 layer
physics has started with them. Besides, the authors have done some incorrect statements which contradict
the present theory of the ionospheric F2 layer.
They claim that
“The topside plasma density is greater in the summer hemisphere than in the winter hemisphere;
… the electron density below the F peak at middle latitudes is also greater during summer than
during winter;
Therefore, the seasonal anomalous behavior is a phenomenon only near the F-peak height in the
Northern Hemisphere;
The question is why the seasonal behavior of the ionosphere near the F-peak height is different from the
behavior below and above the F peak.
….there was no explanation for the different seasonal behaviors of electron density in the lower F region
and at F-peak height”.
This is the main contents and results of the paper. Let us consider what was known about winter anomaly
before the paper by Lee et al. [2011].2014-09-03T22:00:00ZA method for foF2 short-term (1–24 h) forecast using both historical and real-time foF2 observations over European stations: EUROMAP model
http://hdl.handle.net/2122/9179
Title: A method for foF2 short-term (1–24 h) forecast using both historical and real-time foF2 observations over European stations: EUROMAP model
Authors: Perrone, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Mikhailov, A.
Abstract: A method for foF2 short-term forecast over Europe has been developed and implemented in
the EUROMAP model. The input-driving parameters are 3 h ap indices (converted to ap(τ)), effective
ionospheric T index, and real-time foF2 observations. The method includes local (for each station)
regression storm models to describe strong negative disturbances under ap(τ)>30 and training models to
describe foF2 variations under ap(τ) ≤ 30. The derived model was tested in two regimes: descriptive when
observed 3 h ap indices were used and real forecast when predicted daily Ap were used instead of 3 h ap
indices—. In the case of strong negative disturbances the EUROMAP model demonstrates on average the
improvement over the lnternational Reference Ionosphere STORM-time correction model (IRI(STORM))
model: 40% in winter, 24% in summer, and 39% in equinox. The average improvement over climatology is
41% in winter, 59% in summer, and 55% in equinox. In the majority of cases this difference is statistically
significant. In the case of strong positive disturbances, higher-latitude stations also manifest a significant
difference between the twomodels but this difference is insignificant at lower latitude stations. The substitution
of 3 h ap input indices for the predicted daily Ap ones decreases the foF2 prediction accuracy in the case of
negative disturbances but practically has no effect with positive disturbances. In both cases the proposed
method manifests better accuracy than the IRI(STORM) model provides. The obtained results show a real
opportunity to provide foF2 forecast with the (1–24 h) lead time on the basis of predicted Ap indices2014-04-09T22:00:00ZSporadic E layer at mid-latitudes: average properties and influence of atmospheric tides
http://hdl.handle.net/2122/9158
Title: Sporadic E layer at mid-latitudes: average properties and influence of atmospheric tides
Authors: Pignalberi, A.; Dipartimento di Fisica, Università "La Sapienza" di Roma; Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: This paper describes a study of the daily variability shown by the main characteristics of the sporadic
E (Es) layer, that is the top frequency (ftEs) and the lowest virtual height (h’Es). The study is based on ionograms recorded by the Advanced Ionospheric Sounder by the Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed in the ionospheric stations at Rome
(41.8° N, 12.5° E) and Gibilmanna (37.9° N, 14.0° E), Italy, during the summer (June, July, August and September) of 2013, a year falling in the ascending phase of solar cycle 24. The ftEs presents a diurnal variation characterized by two maxima, the first around noon is very well defined and the second in the evening/night is much less defined; the amplitude of both maxima decreases from June to September accompanied
by a general decrease of the ftEs values which is more pronounced in the daytime than in the nighttime. h’Es also presents a diurnal variation characterized by two maxima
but, unlike ftEs, these present the same amplitude which is independent from the considered month. Assuming that both ftEs and h’Es trends are influenced by the atmospheric tides, the height–time–intensity (HTI) technique was applied to deeply investigate how these waves control the Es dynamics. The HTI study, along with a fast Fourier transform analysis, show that a well-defined semidiurnal periodicity characterizes the Es layer dynamics most accurately in June and July, while in August and September the daytime semidiurnal
periodicity becomes weaker and the role of the diurnal periodicity is consequently highlighted.2014-11-20T23:00:00ZRay 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.2014-10-22T22:00:00ZA comparative sporadic-E layer study between two mid-latitude ionospheric stations,
http://hdl.handle.net/2122/9106
Title: A comparative sporadic-E layer study between two mid-latitude ionospheric stations,
Authors: 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: Hourly systematic measurements of the highest frequency reflected by the sporadic-E layer (foEs) recorded from January 1976 to June 2009 at the ionospheric stations of Rome (Italy, 41.8 N, 12.5 E) and Gibilmanna (Italy, 37.9 N, 14.0 E) were considered to carry out a comparative study between the sporadic E layer (Es) over Rome and Gibilmanna. Different statistical analysis were performed taking into account foEs observations near the periods of minimum and maximum solar activity. The results reveal that: (1) independently from
the solar activity, Es develops concurrently over extended regions in space, instead of being a spatially limited layer which is transported horizontally by neutral winds over a larger area; especially during summer months, when an Es layer is present at Rome, there is a high probability that an Es layer is also present over Gibilmanna, and vice versa; (2) Es layer lifetimes of 1–5 h were found; in particular, Es layers with lifetimes of 5 h both over Gibilmanna and Rome are observed with highest percentages of occurrence in summer ranging
between 80% and 90%, independently from the solar activity; (3) latitudinal effects on Es layer occurrence emerge mostly for low solar activity during winter, equinoctial, and summer months, when Es layers are detected more frequently over Gibilmanna rather than Rome; (4) when the presence of an Es layer over Rome and Gibilmanna is not simultaneous, Es layer appearance both over Rome and Gibilmanna confirms to be a locally confined event, because drifting phenomena from Rome to Gibilmanna or vice versa have
not been emphasized.2014-07-14T22:00:00ZThe 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.2014-10-14T22:00:00ZShort-term forecasting regional model to predict M(3000)F2 over the European sector: Comparisons with the IRI model during moderate, disturbed, and very disturbed geomagnetic conditions
http://hdl.handle.net/2122/9103
Title: Short-term forecasting regional model to predict M(3000)F2 over the European sector: Comparisons with the IRI model during moderate, disturbed, and very disturbed geomagnetic conditions
Authors: Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: The hourly measurements of M(3000)F2 (M(3000)F2meas) and the hourly quiet-time values of M(3000)F2 (M(3000)F2QT) relative to
the ionospheric observatories of Poitiers, Lannion, Dourbes, Slough, Rome, Juliusruh, Kaliningrad, Uppsala, Lyckesele, Sodankyla, and Kiruna as well as the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap (ap(s)), were considered during the period January 1957–December 2003 and used for the development of 11 short-term forecasting local models (STFLM) of M(3000)F2.
Under the assumption that the ionospheric disturbance index ln(M(3000)F2meas/M(3000)F2QT) is correlated to the integrated geomagnetic index ap(s), a set of regression coefficients were established over 12 months and 24 h for each of the 11 observatories under consideration
and used as input to calculate the short-term ionospheric forecasting of M(3000)F2 for three different ranges of geomagnetic activity. The 11 short-term forecasting local models all together constitute a single short-term forecasting regional model (STFRM) of
M(3000)F2. The monthly median predictions of M(3000)F2 provided by the IRI model at the 11 local stations were used to make some comparisons with the predictions of M(3000)F2 carried out by the STFRM.
The results showed that: (1) under moderate geomagnetic activity there are no significantly differences between STFRM and IRI performance because quiet geomagnetic conditions are not so diverse from moderate geomagnetic conditions; (2) under disturbed geomagnetic activity, performances of STFRM significantly better than IRI emerge only in some cases; (3) the STFRM’s performances are
always significantly better than those provided by IRI under very disturbed geomagnetic activity, consequently the operative use of the STFRM could be valuable in providing short-term forecasting maps of M(3000)F2 over the European area during very disturbed geomagnetic conditions.2014-07-14T22:00:00ZComment on “Temporal and spatial precursors in ionospheric total electron content of the 16 October 1999 Mw7.1 Hector Mine earthquake”, by Su et al. (2013)
http://hdl.handle.net/2122/9101
Title: Comment on “Temporal and spatial precursors in ionospheric total electron content of the 16 October 1999 Mw7.1 Hector Mine earthquake”, by Su et al. (2013)
Authors: Masci, F; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Thomas, J. N.; NorthWest Research Associates, Redmond, Washington, USA
Abstract: We review the recent paper by Su et al. [2013]. Using Global Position System (GPS) and Global Ionospheric Maps (GIM) data, Su et al. claimed to have found ionospheric precursors a few days before the 16 October 1999 Hector Mine, California earthquake. They proposed that this type of analysis of ionospheric data may be useful for locating forthcoming large earthquakes. In this Comment, we reexamine these data and show that ionospheric anomalies reported by Su et al. were not precursors to the Hector Mine earthquake. Therefore, their proposed analysis is not useful in the context of earthquake prediction.2014-08-07T22:00:00ZUnusual nighttime impulsive enhancements of electron density characterizing the low-latitude ionosphere: Phenomenology and possible mechanisms of triggering
http://hdl.handle.net/2122/9092
Title: Unusual nighttime impulsive enhancements of electron density characterizing the low-latitude ionosphere: Phenomenology and possible mechanisms of triggering
Authors: Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: Unusual nighttime impulsive electron density enhancements that are rarely observed at low latitudes on a wide region of South America are here investigated. These phenomena are very atypical because besides being of brief
duration, they are characterized by a pronounced compression of the ionosphere.
The events were studied and analyzed using both the F2 layer critical frequency (foF2) and the lowest virtual height of the ordinary trace of the F region (h'F) values
recorded at five ionospheric stations widely distributed in space. A careful analysis
of isoheight ionosonde plots suggests that traveling ionospheric disturbances (TIDs)
caused by atmospheric gravity wave (AGW) propagation could play a significant
role in causing these phenomena, both for quiet and for medium-high geomagnetic
activity; in the latter case however a nocturnal recharging of the fountain effect, due to electric fields penetrating from the magnetosphere, plays an as much significant
role.2014-08-31T22:00:00Z