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Leitinger, R.
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Leitinger, R.
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- PublicationOpen AccessRelations between electron contentand peak density: regular and extreme behaviour(2004)
; ; ; ; ; ;Leitinger, R.; Institute of Physics, Institute for Geophysics, Astrophysics and Meteorology (IGAM), University of Graz, Austria ;Ciraolo, L.; Istituto di Fisica Applicata «Nello Carrara» (IFAC), Firenze, Italy ;Kersley, L.; University of Wales, Aberystwyth, U.K. ;Kouris, S. S.; Department of Electrical and Computer Engineering, Aristotelian University of Thessaloniki, Greece ;Spalla, P.; Istituto di Fisica Applicata «Nello Carrara» (IFAC), Firenze, Italy; ; ; ; Electron content statistics offers important information for planning and operation of various application systems that make use of the transionospheric propagation of radio signals. Electron content statistics meet with an important difficulty: the majority of data stem from observations on the radio signals of orbiting satellites. The database for vertical electron content derived from observations of radio signals emitted from geostationary satellites is only very small. Therefore it is important to make use of statistics for peak density from ionosonde measurements. Quantile statistics do not contain information about ionization extremes. Therefore it is necessary to complement the statistics with case studies which reveal unusual and extreme electron content structures in space and in time.218 489 - PublicationOpen AccessProperties of the main trough of the F region derived from Dynamic Explorer 2 data(2002)
; ; ;Feichter, E.; Institut für Geophysik, Astrophysik und Meteorologie, Karl-Franzens-Universität Graz, Austria Institut für Geophysik, Astrophysik und Meteorologie, Karl-Franzens-Universität Graz, Austria" ;Leitinger, R.; Institut für Geophysik, Astrophysik und Meteorologie, Karl-Franzens-Universität Graz, Austria Institut für Geophysik, Astrophysik und Meteorologie, Karl-Franzens-Universität Graz, Austria"; In winter and equinoctial season nights, the main trough of the F region is an important stable structure of the ionosphere at the border between mid and high latitudes. Therefore it has to be taken into account in modelling and mapping approaches. Werner and Prölss (1995) derived a model for the position of the trough minimum which has found wide acceptance. The model is based on in-situ electron density data measured aboard the low orbiting Dynamic Explorer satellite DE 2 (1981-1986). We present results for other properties of the main trough derived from the same data set. These results are sufficiently good for modelling purposes which need reliable information on the depth, the equatorward and poleward width and the steepness of the walls of the trough. Because of the eccentric orbit of DE 2 (orbit height between about 300-1000 km) it was necessary to «project» observed electron densities to the peak of the F 2 layer. This was done by means of the electron density model COSTprof. The database was restricted to those cases for which the height of DE 2 was below 700 km. Examples are shown for «typical» troughs observed under various conditions.139 156 - PublicationOpen AccessTotal electron content - A key parameterin propagation: measurement and usein ionospheric imaging(2004)
; ; ; ; ; ; ; ; ; ; ;Kersley, L.; University of Wales, Aberystwyth, U.K. ;Malan, D.; University of Wales, Aberystwyth, U.K. ;Pryse, S. E.; University of Wales, Aberystwyth, U.K. ;Cander, L. R.; Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, U.K. ;Bamford, R. A.; Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, U.K. ;Belehaki, A.; National Observatory, Institute for Space Applications and Remote Sensing, P. Penteli, Athens, Greece ;Leitinger, R.; Institute of Physics, Institute for Geophysics, Astrophysics and Meteorology (IGAM), University of Graz, Austria ;Radicella, S. M.; The Abdus Salam International Centre for Theoretical Physics (ICTP), Aeronomy and Radiopropagation Laboratory, Trieste, Italy ;Mitchell, C. N.; University of Bath, U.K. ;Spencer, P. S. J.; University of Bath, U.K.; ; ; ; ; ; ; ; ; The paper reports on a series of studies carried out within the COST 271 Action relating to the measurement and use of Total Electron Content (TEC) of the ionosphere over North West Europe. Total electron content is a very important parameter for the correction of propagation effects on applied radio systems so that it is vital to have confidence in the experimental measurements and the resultant products derived as aids for the practical user. Comparative investigations have been carried out using TEC values from several different sources. It was found that in general there was broad statistical agreement between the data sets within the known limitations of the techniques, though discrepancies were identified linked to steep ionospheric gradients at the onset of geomagnetic storm disturbance and in the vicinity of the main trough. The paper also reviews recent progress in the development of tomographic inversion techniques that use total electron content measurements to image the ionosphere as an aid to various radio systems applications.298 2207 - PublicationOpen AccessBehaviour of large scale structures of the electron content as a key parameterfor range errors in GNSS applications(2004)
; ; ; ;Jakowski, N.; Deutsches Zentrum für Luft und Raumfahrt (DLR), Institut für Kommunikation und Navigation (IKN), Neustrelitz, Germany ;Leitinger, R.; Institute of Physics, Institute for Geophysics, Astrophysics and Meteorology (IGAM), University of Graz, Austria ;Ciraolo, L.; Istituto di Fisica Applicata «Nello Carrara» (IFAC), Firenze, Italy; ; The Total Electron Content (TEC) of the ionosphere is a key parameter for describing the ionospheric state. This paper deals with the large scale behaviour of TEC under low and high solar activity conditions. Large scale structures of the plasma density are formed by fundamental ionospheric processes mainly driven by solar radiation input, neutral winds and electric fields. The monitoring of large scale structures contributes to a comprehensive understanding of these coupling mechanisms which are rather complex particularly under perturbed geomagnetic conditions. The paper addresses techniques to monitor TEC with sufficient accuracy of a few TEC units (1016m-2) to measure large scale structures over Europe and over the polar areas. The availability of GPS data from global GPS receiver networks as e.g., those from the International GPS Service (IGS) is dense enough to generate TEC maps on a continuous base. A model assisted technique is briefly described for mapping TEC over the European and polar areas. A statistical estimation of horizontal TEC gradients reveals large scale gradients of up to about 6 TECU/1000 km under high solar activity conditions at an occurrence probability level of about 1%. Occasionally, during severe ionospheric storms this value may increase by a factor of 10 or even more. A close correlation of large scale gradients and the geomagnetic activity has been found giving the chance to forecast TEC gradient amplitudes by using predicted geomagnetic indices. Since TEC is proportional to first-order range errors in Global Satellite Navigation Systems (GNSS) such as the US GPS and the Russian GLONASS the study of the behaviour of this parameter has a practical meaning in GNSS based navigation and positioning. The paper addresses the close relationship between TEC and ranging errors in GNSS. Having in view Galileo, the planned Europe’s own global satellite navigation system, some aspects related to the mitigation of ionospheric propagation errors within the European Geostationary Navigation Overlay System (EGNOS) are discussed. Since EGNOS will augment the two above mentioned satellite navigation systems and make them suitable for safety critical applications such as flying aircraft or navigating ships through narrow channels the ionospheric propagation errors have to be mitigated as much as possible.170 560 - PublicationOpen AccessRadio occultation techniques for probing the ionosphere(2004)
; ; ; ;Jakowski, N.; Deutsches Zentrum für Luft und Raumfahrt (DLR), Institut für Kommunikation und Navigation (IKN), Neustrelitz, Germany ;Leitinger, R.; Institute of Physics, Institute for Geophysics, Astrophysics and Meteorology (IGAM), University of Graz, Austria ;Angling, M.; Centre for RF Propagation and Atmospheric Research, QinetiQ, Malvern, U.K.; ; GPS radio occultation measurements establish the basis for a new remote sensing technique for vertical profile information on the electron density of the entire ionosphere from satellite orbit heights down to the bottomside. No other profiling technique such as vertical sounding or incoherent scatter, unifies vertical profiling through the entire ionosphere with global coverage. Inversion methods are described both for vertical profiling as well as for tree dimensional electron density reconstructions of the ionosphere. In three dimensional electron density reconstructions using signals from Global Navigation Satellite Systems (GNSS), the Ionospheric Radio Occultation (IRO) measurements provide vertical information which is complementary to the information obtained by ground based measurements. Assessment of achievable accuracy and spatial resolution are addressed by simulation studies. IRO measurements have been carried out onboard the German CHAMP satellite since 11 April 2001 on a routine basis. Assuming a spherically layered ionosphere, up to about 150 Electron Density Profiles (EDPs) per day are retrieved within a latency of 3 h. Validation results obtained by using independent data sources are reported. The validation with vertical sounding data in mid-latitudes indicates a small positive bias in the plasma frequency of up to about 0.5 MHz throughout the entire profile. Averages of the numerous EDPs show wellknown ionospheric phenomena such as the equatorial anomaly, the winter anomaly and the expansion of the profile with increasing solar energy input. It is concluded that CHAMP-IRO measurements have the potential to establish global data sets of vertical electron density profiles for developing and improving global ionospheric models and to provide operational space weather information.204 856 - PublicationOpen AccessAn improved bottomside for the ionospheric electron density model NeQuick(2005)
; ; ; ;Leitinger, R.; Institut für Physik, Institutsbereich für Geophysik, Astrophysik und Meteorologie (IGAM), Universität Graz, Austria ;Zhang, M. L.; Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, People s Republic of China ;Radicella, S. M.; The Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy; ; 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.426 4132 - PublicationOpen AccessAssessment of space plasma effectsfor satellite applications:Working Group 2 overview(2004)
; ; ;Leitinger, R.; Institute of Physics, Institute for Geophysics, Astrophysics and Meteorology (IGAM), University of Graz, Austria ;Jakowski, N.; Deutsches Zentrum für Luft und Raumfahrt (DLR), Institut für Kommunikation und Navigation (IKN), Neustrelitz, Germany; An important part of the tasks of Working Group 2 of the COST Action 271 «Assessment of space plasma effect for satellites applications» is the assessment of novel data sources for information about the state of ionisation of the ionosphere. This report deals with those aspects which are not represented adequately in the scientific papers in this issue. Here emphasis is given to the product aspect (data and model collections, descriptions of methods and algorithms, availability of products, expected future developments) and the links between the past COST Actions 238 and 251 with the present Action 271 and with possible future cooperations. Working Group 2 was leading in the transionospheric propagation aspects of possible products for the International Telecommunication Union’s Radiocommunication (ITU-R) Study Group 3. This report gives a short overview emphasizing future developments.141 244 - PublicationOpen AccessThe TID model for modulation of large scale electron density models(2005)
; ; ;Leitinger, R.; Institut für Physik, Institutsbereich für Geophysik, Astrophysik und Meteorologie (IGAM), Universität Graz, Austria ;Rieger, M.; Institut für Physik, Institutsbereich für Geophysik, Astrophysik und Meteorologie (IGAM), Universität Graz, Austria; 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).239 481 - PublicationOpen AccessIonospheric electron content: the European perspective(1998-11)
; ;Leitinger, R.; Institut für Meteorologie und Geophysik, Universität Graz, AustriaThe electron content of the ionosphere is an important quantity which indicates overall ionization. It is measured by means of propagation effects on radio signals which penetrate the ionosphere. In Europe relevant investigations started after the launch of the first artificial satellites. Soon the necessity arose to organize international cooperation: the regional as well as the global geographical distribution of ionization parameters is important knowledge for any meaningful geophysical interpretation of ionization parameters. Despite the fact that international scientific Unions and Committees existed and had proven their usefulness and potential, private initiatives were taken to organize cooperation in the field of research based on transionospheric propagation effects. Only in 1971 three international groups joined together to form the "Beacon Satellite Group"as a "Working Party" of COSPAR. The "Beacon Satellite Group" still exists but is now a Working Group of URSI, the International Union for Radio Science. This contribution tries to summarize the European perspective with special emphasis on the long standing cooperation between the Istituto di Ricerca sulle Onde Elettromagnetiche (IROE) at Firenze and the Institut für Meteorologie und Geophysik of the University of Graz. Examples are given of important results.167 437