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SPACE WEATHER, VOL. 8, S02001, doi:10.1029/2009SW000493, 2010
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Monitoring and modeling of ionospheric characteristics in the framework of European COST 296 Action MIERS Iwona Stanislawska,1 Jan Lastovicka,2 Alain Bourdillon,3 Bruno Zolesi,4 and Ljiljana R. Cander5 Received 11 May 2009; revised 14 October 2009; accepted 3 November 2009; published 20 February 2010.
[1] The Mitigation of Ionospheric Effects on Radio Systems COST 296 Action is devoted to the mitigation of ionospheric effects on radio systems. It creates a platform for sharing of data, algorithms, models, and jointly developed advanced technologies, the processing chain from measurements, through algorithms, to operational knowledge. This initiative creates a unique possibility for national groups to consolidate the design of a product required for their own activity and for European assessments in the ionosphere and telecommunication area. An important part of the action is to stimulate and integrate many national and international activities which provide tools for global and regional ionospheric monitoring and modeling. The work includes the near-Earth space plasma monitoring, modeling and forecasting, and a study of the upper atmosphere climate. Well-defined terms of reference include developing ground-based and space-borne monitoring techniques and parameters describing the state of ionospheric plasma, maintaining and extending the flow of real-time and retrospective ionospheric monitoring data to databases. To obtain adequate, high-quality information, special attention is paid to the data ingestion and assimilation in constructing ionospheric models of different spatial and time scale perturbations, as well as storms, small variations, and irregularities. The physical origin of atmospheric/ionospheric effects and their signatures and parameters are investigated. Identification criteria are studied and formulated. Citation: Stanislawska, I., J. Lastovicka, A. Bourdillon, B. Zolesi, and L. R. Cander (2010), Monitoring and modeling of ionospheric characteristics in the framework of European COST 296 Action MIERS, Space Weather, 8, S02001, doi:10.1029/ 2009SW000493.
1. Introduction [2] The ionosphere is formed in the upper part of the Earth’s atmosphere as a result of radiation from the Sun. Thus, the ionosphere experiences changes in different time scales, depending on long-term and short-term solar activity as well as atmosphere (thermosphere) dynamics. Solar cycle activity, solar wind and geomagnetic disturbances, solar location relative to the Earth, and winds in the upper atmosphere are relevant elements of forming the ionosphere. The ionosphere is a dispersive medium and affects the electromagnetic signals that pass through it by inducing a transmission time delay, signal fadeout and refraction. The magnitude of this effect is determined by the electron density as a function of altitude. For example, 1
Space Research Centre, PAS, Warsaw, Poland. Institute of Atmospheric Physics, Prague, Czech Republic. IETR, University of Rennes 1, Rennes, France. 4 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy. 5 Rutherford Appleton Laboratory, Didcot, UK. 2 3
Copyright 2010 by the American Geophysical Union
the ionosphere effect has become the largest error source in satellite positioning and navigation. The solar radiationatmosphere-ionosphere coupling is nonlinear and, in order to follow it, a combination of measurement and sophisticated modeling for different conditions is necessary. Thus, in the context of space weather needs, operational meteorology and telecommunication, the operational model of ionospheric electron density profiles is crucial. [3] European activity related to this subject has been realized within the COST (European Cooperation in Science and Technology) organization, which is devoted to science and its application. The COST 296 Action ‘‘Mitigation of Ionospheric Effects on Radio Systems’’ (MIERS) is a 4 year project launched in 2005. Cooperative research on mitigation of effects of the ionosphere on radio systems at the European level is absolutely necessary because accurate propagation of information is essential to support the design, implementation and operation of most modern terrestrial and satellite communication
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systems. Advances in achieving mitigation, monitoring, prediction and forecasting of ionospheric effects should be accomplished by bringing together groups working with radio engineering applications oriented objectives and groups that give more emphasis to radio science. Currently, there is no structured coordination effort in Europe in this domain outside COST. The earlier COST actions relating to ionospheric radio propagation were focused on building ionospheric regional maps and models, such as COST 238 PRIME (Prediction and Retrospective Ionospheric Modeling over Europe) [Bradley, 1995], application of PRIME results in the improved quality service in ionospheric telecommunication systems planning and operation in COST 251 IITS (Improved Quality of Service in Ionospheric Telecommunication Systems Planning and Operation) [Hanbaba, 1999], and effects of the upper atmosphere on terrestrial and Earth-space communication in COST 271 [Zolesi and Cander, 2004]. COST 296 MIERS addresses the above mentioned problems, involving some researchers not attending previous actions which might help in finding the solutions, and creates the necessary area of cooperation. The main objectives of the current action were defined as follows, ‘‘to develop an increased knowledge of the effects imposed by the ionosphere on practical radio systems, and to develop and implement techniques to mitigate the deleterious effects of the ionosphere on such systems,’’ as per the Memorandum of Understanding: (1) to stimulate further cooperation in ionosphere and plasmasphere prediction and forecasting, including interactive repercussions on the corresponding standards in this field, taking into account the current and future user needs; (2) to perform studies to influence the technical development and the implementation of new communication services, particularly for the Global Navigation Satellite System and other advanced Earth-space and satellite-to-satellite applications; (3) to develop methods and algorithms to predict and to minimize the effects of ionospheric perturbations and variations on communications and to ensure that the best models over Europe are made available to the International Telecommunication Union Radiocommunication Sector (ITU-R); and (4) to collect additional and new ionospheric and plasmaspheric data for nowcasting and forecasting purposes. [4] The basis of every COST action is cooperation. The collaboration within COST 296 Action is rich due to many national and international activities which provide instruments and tools for global as well as regional monitoring and modeling. The action stimulates, coordinates and supports European cooperation by providing a platform for organizing different task groups for joint elaboration of reference topics undertaken within the defined terms, sharing the knowledge and experience between participants from different countries and research institutions. This includes sharing of such tools as algorithms or models and jointly developed advanced technologies. [5] The enhancement of environment monitoring networks and associated instruments technology yields
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mutual advantages for European entities specialized in monitoring and modeling of the ionosphere and plasmasphere. It structurally increases their integration, and provides a platform employing a variety of approaches to each task. In doing so, it also provides a complementary description of the environmental state. [6] A general scheme of the monitoring and modeling concept within the COST 296 activity is the processing chain, from measurements, through algorithms to operational knowledge, that mitigates the environmental impact on radio systems. This involves the determination of the required scope of information, identification of tools necessary to obtain it, and the means for processing and tailoring it for specific system’s needs. Such an initiative offers a unique possibility for every European participant to consolidate the design of a product required not only for his own activity, but also for panEuropean use. [7] Guaranteed open access to the results of the action facilitates further development of the European scientific and technical basis. [8] The work in the COST 296 Action is organized in three Working Groups. The aim of this paper is to review the main results achieved by COST 296 working group WG-1, Ionospheric monitoring and modeling.
2. Organization [9] The work is arranged in three Working Groups under specified topic headings. [10] 1. Working Group 1 is ionospheric monitoring and modeling. Subgroups are WP1.1, near-Earth space plasma monitoring; WP1.2, data ingestion and assimilation in ionospheric models; WP1.3, near-Earth space plasma modeling and forecasting; and WP1.4, climate of the upper atmosphere. [11] 2. Working Group 2 is advanced terrestrial systems. Subgroups are WP2.1, radar and radiolocation; WP2.2, HF/MF communications; and WP2.3, spectrum management. [12] 3. Working Group 3 is space based system. Subgroups are WP3.1, space plasma effects; WP3.2, mitigation techniques; and WP3.3, scintillation monitoring and modeling. [13] Working Group 1 is focused on ionospheric monitoring and modeling with detailed specification as follows: (1) near-Earth space plasma monitoring by vertical incidence and oblique sounding networks and Global Navigation Satellite System (GNSS) techniques (retrospective and real-time); (2) data ingestion and assimilation into ionospheric models, including data collection and processing, and the adaptation of models to enable data ingestion and assimilation; (3) near-Earth space plasma modeling and forecasting including mitigation of ionospheric perturbations, and tomographic imaging for model validation; and (4) the climate of the upper atmosphere including long-term ionospheric trends, ionospheric vari-
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ability, gravity and planetary wave affects on propagation and ionospheric space weather. [14] Well-defined terms of reference include developing ground-based and space-borne monitoring techniques and parameters describing the state of ionospheric plasma, maintaining and extending the flow of realtime and retrospective ionospheric monitoring data to databases, validating the quality and consistency of the data, particularly those collected in real time, and developing the protocols for disseminating data products.
3. Main Results of the Action
Figure 1. Ionograms for 9 April 2008, 0900, 1700, and 2000 UT from VISRC2 ionosonde at Warsaw station (52.2°N, 21.1°E) with characteristics obtained by means of Autoscala software and manually corrected.
[15] Continuously enriched Internet databases located at RAL (Rutherford Appleton Laboratory, UK) http:// www.ukssdc.rl.ac.uk/prompt_database.html, IZMIRAN (Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation Russian Academy of Science) (http:// www.izmiran.ru/ionosphere/weather), and IDCE (Ionospheric Despatch Centre in Europe, Poland) (http:// www.cbk.waw.pl/rwc), yield data sharing and exchange. On the other hand, validating the quality and consistency of data monitoring, particularly those collected in real time, are the topics that many teams are focused on. Ionospheric characteristics are made available in near -real time, such as soundings presented in Figure 1 obtained with newly developed ionosonde VISRC2 (Space Research Centre, Poland), where characteristics are extracted by means of Autoscala software and manually corrected two times a day. Autoscala, a computer program for the automatic scaling designed to be applied to the ionosonde AIS (Advanced Ionospheric Sounder), was developed at INGV (Istituto Nazionale di Geofisica e Vulcanologia, Italy) but can be easily applied to any kind of ionosonde [Pezzopane and Scotto, 2008]. [16] Real-time and revised data provided by means of the ground based electromagnetic probing techniques such as vertical (VI) and oblique incidence sounding for comparison and validating studies are available at web sites of some stations, e.g., http://www.obsebre.es/php/ ionosfera.php (Spain). [17] Ionospheric activity indices derived from automatically scaled online data from several European ionosonde stations have been used to distinguish between normal ionospheric conditions and ionospheric disturbances caused by specific solar and atmospheric events (flares, coronal mass ejections, atmospheric waves, etc.). The ionospheric disturbance level over a substantial part of Europe (34°N -- 60°N; 5°W -- 40°E) can now be displayed online [Bremer et al., 2006]. Planetary and zonal indices of the ionosphere variability derived from numerical maps of foF2 as well as TEC (Total Electron Content) have been calculated [Gulyaeva and Stanislawska, 2008]. [18] Catalogues of ionospheric disturbed periods, and disturbed and quiet ionospheric days are available online (http://www.cbk.waw.pl/rwc/). [19] A cooperating team among the COST community evaluated the response of the ionosphere/thermosphere 3 of 7
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Figure 2. Best values for the correction factor of the NeQuick bottomside F2 layer thickness parameter at Millstone Hill (42.6°N, 71.5°W) as a function of UT for the day 26 March 2000. caused by solar radiation changes during the annular solar eclipse of October 2005 over Europe. The ionospheric plasma redistribution processes related to this event significantly affect the shape of electron density profile. Excitation of gravity waves has been observed. These processes were discussed based on a comparison of vertical sounding and vertical total electron content (TEC) data above selected ionosonde stations in Europe. Ionosonde and HF Doppler measurements revealed enhanced wave activity but the TEC data did not [Jakowski et al., 2008]. Several COST 296 stations also performed a rapid VI sounding campaign on the occasion of the total solar eclipse of March 2006. [20] New models of electron concentration have been elaborated and a substantial improvement of the earlier tools has been achieved. Examples are EDAM (Electron Density Assimilative Model), and a new formulation of the NeQuick topside profile. A new version of the NeQuick model has been formulated [Nava et al., 2008]. The NeQuick topside profile developed on the basis of ISIS 2 topside sounder data and incorporated into IRI (International Reference Ionosphere) for inclusion in the IRI 2006 version was adopted by the ITU-R Group for telecommunication practice. The flexibility of this model to incorporate small-scale ionospheric structures makes it a useful tool for ray-tracing propagation modeling developed on the basis of ISIS 2 topside sounder data and adopted by IRI for inclusion in the IRI 2006 version, as one of the
options for calculation of electron density profile and TEC [Nava et al., 2006]. Figure 2 shows the values of the correction factor of the NeQuick bottomside F2 layer thickness parameter at Millstone Hill as a function of UT for 26 March 2000. These values are computed adapting the model to slant TEC and foF2 values in the area of interest. EDAM [Angling and Khattatov, 2006] provides a means to assimilate measurements into a background ionospheric model. The assimilation is based on a weighted, damped least mean squares estimation. This is a form of minimum variance optimal estimation (also referred to as the Best Linear Unbiased Estimation, BLUE), which provides an expression for an updated estimation of the state that is dependent upon an initial estimate of the state (the background model), and the differences between the background model and the observations. An example of results for foF2 for September 2006 is shown in Figure 3 for the ionosonde at Wallops Island. [21] Many other models and improvement of real-time or near-real-time electron density reconstruction techniques have been developed. For these purposes sets of very high quality experimental data (such as TEC and ionospheric parameters), as well as ‘‘synthetic’’ data (produced by means of a model) for model validation and data ingestion studies were prepared. [22] Warning, nowcasting and forecasting models developed within the current action describe space plasma and propagation, as well as their different scale perturbations 4 of 7
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Figure 3. Median values of foF2 and EDAM errors for Wallops Island (37.9°N, 75.5°W). by means of neurofuzzy and other novel techniques. Particular attention is paid to their drivers. Comparison of the topside ionosphere scale height determined by the topside sounders model and bottomside Digisonde profiles [Belehaki et al., 2006] and topside thickness [Gulyaeva, 2007] facilitates development of further models. Modeling of the behavior of the neutral scale height Hm at hmF2 (the F2 peak) that has been deduced from electron density profiles N(h) is an example of contributing models. [23] Data from the International Global Navigation Satellite Systems Service have been used to study the development of TEC fluctuations at the high-latitude ionosphere. GPS (Global Positioning System) observations covering the auroral and polar ionosphere were made to investigate the occurrence of TEC fluctuations, dependent upon geomagnetic activity [Krankowski and Shagimuratov, 2006]. [24] Spatial and temporal analysis of the medium-scale traveling ionospheric disturbances affecting GPS measurements [Herna´ndez-Pajares et al., 2006] presented an important example of the climatological approach. [25] The ionospheric scale height model based on data accumulated from the CHAMP satellite (Challenging Minisatellite Payload) mission is an example of a model that can be implemented into an iterative retrieval procedure by delivering an improved initial guess [Stankov and Jakowski, 2006]. [26] A new assimilation procedure of ground-based and occultation GPS TEC data into a combined IRI/GCPM (Guard Channel Prediction Model) model has been developed. The accuracy of the resulting electron density fields is markedly better through the assimilation of the GPS data, as shown by comparison with the soundings of seven European ionosonde stations [Stolle et al., 2006]. [27] The ionospheric forecasting empirical local model over Rome (IFELMOR) to predict the state of the critical
frequency of the F2 layer (foF2) during strong geomagnetic storms and disturbed ionospheric conditions is an example of ionospheric disturbance forecasting [Perrone et al., 2007]. [28] The time/altitude variability of electron density as ionospheric characteristics and/or TEC describes the morphology, so that it is the basis for prediction and forecasts [Fotiadis and Kouris, 2006; Kouris et al., 2006]. A simple model of foF2 variability has been developed by Fotiadis and Kouris [2006]. [29] The model of TEC forecasting constructed by means of an artificial neural network presents a global approach. The Middle East Technical University Neural Network (METU NN) [Tulunay et al., 2006] has been presented as an example of a new technique developed for the purposes of the action. The TEC model has demonstrated the power of forecasting the parameters of a nonlinear process and has also globally described the European area. But only by improving the description of various phenomena as, for instance, the midlatitude ionospheric trough, or the traveling ionospheric and atmospheric disturbances, can the usefulness of the models be proven further. So an important part of the work is a proper description of morphological modeling of the midlatitude ionospheric trough, as done by Pryse et al. [2006]. [30] The global pattern of consistent long-term changes and trends in the upper atmosphere-ionosphere system has been established in broad international collaboration; COST 296 participants developed its ionospheric part. The global pattern consists of trends in neutral mesospheric and mesopause region temperature, neutral thermospheric density, and ionospheric D, E and F1 regions [Lastovicka et al., 2006a]. These trends at least qualitatively agree with those expected as a result of the increasing greenhouse gas concentration and related upper atmospheric cooling and contraction. Trends in the F2 layer remain controversial; it is possible that long-term changes of 5 of 7
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Figure 4. The foF2 forecast for Kokubunji station (N 36°, E 139°) by means of K Nearest Neighbor NN algorithm developed within the COST 296 Action. geomagnetic activity play a more important role than the greenhouse effect for this case [Lastovicka et al., 2006b; Mikhailov, 2006]. However, all these changes are relatively weak, long term and slow and, therefore, do not play a role in ionospheric forecasting. They can affect to some extent only long-term predictions and planning.
4. Scientific Results Applicable for Operational Use [31] COST 296 also provides a platform for sharing such tools as algorithms or models, and for the joint development of advanced technologies. The main benefits derived from these are the added value products applicable to the current and new generation of radio systems operated in, or affected by, the near-Earth plasma environment. It takes advantage of many national and European service initiatives, including DIAS (European Digital upper Atmosphere Server) (http://dias.space.noa.gr), SWACI (Space Weather Application Center -- Ionosphere) (http:// w3swaci.dlr.de), ESWUA (Electronic Space Weather Atmosphere) (http://www.eswua.ingv.it/ingv), Regional Warning Centre of the International Space Environment Service Warsaw (http://www.cbk.waw.pl/rwc), the COST Prompt Ionospheric Database http://www.wdc.rl.ac.uk/ cgi-bin/digisondes/cost_database.pl, http://www.izmiran. ru/services, and others. [32] The results from the action are implemented in the computer programs prepared to provide wide information about ionospheric and plasmaspheric conditions supporting HF radio communication in accordance with the COST 296 Mission Statement [Stanislawska et al., 2009]. Access to near-real-time information on ionospheric conditions over Europe is indispensable for high-frequency radio communication. The use of this information by currently operating services needs a number of adaptations and adjustments. Some of them are direct action issues; others are the responsibilities of the services’ owners. The action itself proposes useful and convenient approaches, and new algorithms generate novel directions for the operational services. The examples of applications available in the near -- real time in currently existing systems devoted to specialized users concern near-real-time
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mapping and forecasting of ionosphere conditions, as disturbance forecasting empirical model IFELMOR applied in ESWUA system [Romano et al., 2008], SIRMUP in DIAS, ‘‘K Nearest Neighbor NN algorithm’’ in RWC Warsaw (Figure 4), TEC forecasting in SWACI, or nearreal-time ionospheric warning index at DIAS service. Next applications are under development. Validation of the mapping and forecasting algorithms has been presented by Cander [2008]. [33] The knowledge of current and predicted ionospheric conditions and their possibly threatening effects on space systems enables decision makers, planners and operators to gain, mitigate, and maintain space superiority across the spectrum of conflict or disaster scenarios. The mitigation techniques developed and improved by the COST 296 Action and implemented in users’ services prepare these services to operate better and more efficiently.
5. Concluding Remarks [34] In spite of the considerable progress achieved, various open questions remain to be addressed in future investigations. The action is in progress, so the next step in the development of more accurate achievements is ensured. A full description of the action is available at http://www.cost296.rl.ac.uk, together with detailed information about models, measurement facilities provided, and a list of publications and presentations. Information about the action participants is also available at http:// www.cbk.waw.pl/cost296/. [35] COST actions as programs devoted to science and to more application-oriented areas increase the competitiveness of European industry, and contribute to sustainable social development, which constitutes a basis for future existence. For example, from the satellite navigation and telecommunication perspective, the need for the integrity of the modeling of disturbances in ionospheric and tropospheric conditions is obvious (the International Telecommunication Union Radiocommunication Sector). Integrated operational models of the near-Earth space for telecommunication practice should be the focus of future actions. [36] Acknowledgment. The authors would like to thank the COST 296 community for providing the information for this paper, particularly Matthew J. Angling.
References Angling, M. J., and B. Khattatov (2006), Comparative study of two assimilative models of the ionosphere, Radio Sci., 41, RS5S20, doi:10.1029/2005RS003372. Belehaki, A., P. Marinov, I. Kutiev, N. Jakowski, and S. Stankov (2006), Comparison of the topside ionosphere scale height determined by topside sounders model and bottomside Digisonde profiles, Adv. Space Res., 37(5), 963 -- 966, doi:10.1016/j.asr.2005.09.014. Bradley, P. A. (1995), PRIME (Prediction and Retrospective Ionospheric Modelling over Europe), COST Action 238 Final Rep. Adv. Issue, Comm. of the Eur. Communities, Brussels.
6 of 7
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Bremer, J., L. R. Cander, J. Mielich, and R. Stamper (2006), Derivation and test of ionospheric activity indices from real-time ionosonde observations in the European region, J. Atmos. Sol. Terr. Phys., 68(18), 2075 -- 2090, doi:10.1016/j.jastp.2006.07.003. Cander, L. R. (2008), Ionospheric research and space weather services, J. Atmos. Sol. Terr. Phys., 70(15), 1870 -- 1878, doi:10.1016/ j.jastp.2008.05.010. Fotiadis, D. N., and S. S. Kouris (2006), A functional dependence of foF2 variability on latitude, Adv. Space Res., 37(5), 1023 -- 1028, doi:10.1016/j.asr.2005.02.054. Gulyaeva, T. L. (2007), Variable coupling between the bottomside and topside thickness of the ionosphere, J. Atmos. Sol. Terr. Phys., 69(4 -- 5), 528 -- 536, doi:10.1016/j.jastp.2006.10.015. Gulyaeva, T. L., and I. Stanislawska (2008), Derivation of a planetary ionospheric storm index, Ann. Geophys., 26, 2649 -- 2655. Hanbaba, R. (1999), Improved quality of service in ionospheric telecommunication systems planning and operation, COST 251 Final Rep., Space Res. Cent., Warsaw. Herna´ndez-Pajares, M., J. M. Juan, and J. Sanz (2006), Medium-scale traveling ionospheric disturbances affecting GPS measurements: Spatial and temporal analysis, J. Geophys. Res., 111, A07S11, doi:10.1029/2005JA011474. Jakowski, N., et al. (2008), Ionospheric behavior over Europe during the solar eclipse of 3 October 2005, J. Atmos. Sol. Terr. Phys., 70(6), 836 -- 853, doi:10.1016/j.jastp.2007.02.016. Kouris, S. S., K. Polimeris, and L. Cander (2006), Specifications of TEC variability, Adv. Space Res., 37(5), 983 -- 1004, doi:10.1016/ j.asr.2005.01.102. Krankowski, A., and I. I. Shagimuratov (2006), Impact of TEC fluctuations in the Antarctic ionosphere on GPS positioning accuracy, Artif. Satell., 41(1), 43 -- 56, doi:10.2478/v10018-007-0005-5. Lastovicka, J., R. A. Akmaev, G. Beig, J. Bremer, and J. T. Emmert (2006a), Global change in the upper atmosphere, Science, 314(5803), 1253 -- 1254, doi:10.1126/science.1135134. Lastovicka, J., et al. (2006b), Long-term trends in foF2: A comparison of various methods, J. Atmos. Sol. Terr. Phys., 68(17), 1854 -- 1870, doi:10.1016/j.jastp.2006.02.009. Mikhailov, A. V. (2006), Ionospheric long-term trends: Can the geomagnetic control and the greenhouse hypotheses be reconciled?, Ann. Geophys., 24(10), 2533 -- 2541. Nava, B., S. M. Radicella, R. Leitinger, and P. Coı¨sson (2006), A nearreal-time model-assisted ionosphere electron density retrieval method, Radio Sci., 41, RS6S16, doi:10.1029/2005RS003386. Nava, B., P. Coı¨sson, and S. M. Radicella (2008), A new version of the NeQuick ionosphere electron density model, J. Atmos. Sol. Terr. Phys., 70(15), 1856 -- 1862, doi:10.1016/j.jastp.2008.01.015.
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Perrone, L., M. Pietrella, and B. Zolesi (2007), A prediction model of foF2 over periods of severe geomagnetic activity, Adv. Space Res., 39(5), 674 -- 680, doi:10.1016/j.asr.2006.08.008. Pezzopane, M., and C. Scotto (2008), A method for automatic scaling of F1 critical frequency from ionograms, Radio Sci., 43, RS2S91, doi:10.1029/2007RS003723. Pryse, S. E., L. Kersley, D. Malan, and G. J. Bishop (2006), Parameterization of the main ionospheric trough in the European sector, Radio Sci., 41, RS5S14, doi:10.1029/2005RS003364. Romano, V., S. Pau, M. Pezzopane, E. Zuccheretti, B. Zolesi, G. De Franceschi, and S. Locatelli (2008), The electronic space weather upper atmosphere (eSWua) project at INGV: Advancements and state of the art, Ann. Geophys., 26, 345 -- 351. Stanislawska, I., et al. (2009), COST 296 scientific results designed for operational use: COST 296 final report, Ann. Geophys., 52(3 -- 4), 215 -- 227. Stankov, S. M., and N. Jakowski (2006), Topside ionospheric scale height analysis and modelling based on radio occultation measurements, J. Atmos. Sol. Terr. Phys., 68(2), 134 -- 162, doi:10.1016/ j.jastp.2005.10.003. Stolle, C., S. Schlu¨ter, S. Heise, C. Jacobi, N. Jakowski, and A. Raabe (2006), A GPS based three-dimensional ionospheric imaging tool: Process and assessment, Adv. Space Res., 38(11), 2313 -- 2317, doi:10.1016/j.asr.2006.05.016. Tulunay, E., E. T. Senalp, S. M. Radicella, and Y. Tulunay (2006), Forecasting total electron content maps by neural network technique, Radio Sci., 41, RS4016, doi:10.1029/2005RS003285. Zolesi, B., and L. R. Cander (2004), COST 271 Action---Effects of the upper atmosphere on terrestrial and Earth-space communications: Introduction, Ann. Geophys., 47(2 -- 3), 915 -- 925. A. Bourdillon, IETR, University of Rennes 1, Campus de Beaulieu, F-35042 Rennes CEDEX, France. L. R. Cander, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK. J. Lastovicka, Institute of Atmospheric Physics, Bocni II, 14131 Prague, Czech Republic. I. Stanislawska, Space Research Centre, PAS, Bartycka St. 18a, 00-716 Warsaw, Poland. (
[email protected]) B. Zolesi, Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, I-00143 Rome, Italy.
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