Vol52,3,2009 221 ANNALS OF GEOPHYSICS, VOL. 52, N. 3/4, June/August 2009 Key words Ionosphere – monitoring – data validation – monitoring techniques – campaigns – dissemination 1. Introduction The ionosphere is a rather complex and highly variable medium, and to be able to pre- dict and when necessary mitigate the influence of the ionosphere on radio wave propagation in- cluding signals from the Global Navigation Satellite Systems (GNSS), ionospheric moni- toring measurements are crucial as a necessary basis for studying and understanding the iono- sphere. Real-time data are necessary for operational ionospheric mitigation. Ionospheric monitoring in the European area is done by a network of ionosondes and, in recent years, also by a net- work of high-accuracy Global Positioning Sys- tems receivers (GPS), which work primarily for Near Earth space plasma monitoring under COST 296 David Altadill (1), Josef Boska (2), Ljiljana R. Cander (3), Tamara Gulyaeva (4) (10), Bodo W. Reinisch (5), Vincenzo Romano (6), Andrzej Krankowski (7), Jürgen Bremer (8), Anna Belehaki (9), Iwona Stanislawska (10), Norbert Jakowski (11) and Carlo Scotto (6) (1) Observatori de l’Ebre, Universitat Ramon Llull – CSIC, Spain (2) Institute of Atmospheric Physics, ASCR, Czech Republic (3) STFC, Rutherford Appleton Laboratory, Chilton, UK. (4) IZMIRAN , Troitsk, Moscow Region, Russia (5) Center for Atmospheric Research, UMass Lowell, USA (6) Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy (7) University of Warmia and Mazury, Poland (8) Leibnitz-Institute of Atmospheric Physics, Kühlungsborn, Germany (9) National Observatory of Athens, Athens, Greece (10) Space Research Centre PAS, Warsaw, Poland (11) DLR, Institute of Communications and Navigation, Neustrelitz, Germany Abstract This review paper presents the main achievements of the near Earth space plasma monitoring under COST 296 Action. The outputs of the COST 296 community making data, historical and real-time, standardized and avail- able to the ionospheric community for their research, applications and modeling purposes are presented. The con- tribution of COST 296 with the added value of the validated data made possible a trusted ionospheric monitoring for research and modeling purposes, and it served for testing and improving the algorithms producing real-time data and providing data users measurement uncertainties. These value added data also served for calibration and validation of space-borne sensors. New techniques and parameters have been developed for monitoring the near Earth space plasma, as time dependent 2D maps of vertical total electron content (vTEC), other key ionospheric parameters and activity indices for distinguishing disturbed ionospheric conditions, as well as a technique for im- proving the discrepancies of different mapping services. The dissemination of the above products has been devel- oped by COST 296 participants throughout the websites making them available on-line for real-time applications. Mailing address: Dr. David Altadill, Observatori de l’E- bre, Universitat Ramon Llull – CSIC, Crta. de l’Observatori, No. 8, E43520 - Roquetes, Spain; e-mail daltadill@obsebre.es Vol52,3,2009 20-09-2009 19:05 Pagina 221 222 D. Altadill, J. Boska, L.R. Cander, T. Gulyaeva, B.W. Reinisch, V. Romano, A. Krankowski, J. Bremer, A. Belehaki, I. Stanislawska, N. Jakowski and C. Scotto geodesy and positioning. The COST 296 action joins scientists from all the European institu- tions operating ionosonde systems (vertical ionospheric sounding instruments, essentially radars but the newest being a combination of radar and Doppler interferometer). These systems work in a continuous moni- toring regime, covering essentially the whole of Europe, including Scandinavia’s Sodankyla station. Data from a network of GPS stations have also been used in COST 296 in recent years, as well as radio occultation GNSS meas- urements. The aim of this paper is to review the main results achieved by COST 296 working group WG-1«Ionospheric monitoring and modeling» under the working package WP1.1 «Near Earth space plasma monitoring». The WP1.1 encompassed the ionospheric measurements, data collecting, archiving and dissemination, and development of new meth- ods of ionospheric measurements, monitoring, and conditions characterization. The WP1.1 created an observational basis for the project COST 296 and its work was de- fined by four terms of reference: 1) Maintaining and extending the flow of real-time and retro- spective ionospheric monitoring data to data- bases; 2) Supporting and developing INTER- NET sites and protocols for disseminating data products; 3) Validating the quality and consis- tency of monitoring data, particularly those col- lected in real time; and 4) Developing monitor- ing techniques and parameters describing the state of the ionospheric plasma, to include ground-based and space based techniques. The paper is organized according to these terms of reference and related work. Section 2 summarizes the main efforts for archiving real time and historical databases. Section 3 describes the main results for val- idating the monitoring data. Section 4 reviews the monitoring techniques and parameters describing the state of the ionos- pheric plasma developed within the project. Section 5 highlights the main efforts for dis- seminating data and added value products. Fi- nally, Section 6 presents results from the specif- ic COST 296 campaigns. The paper ends with a summary. 2. Real-time and historical databases The European ionospheric community has been working for long time on several COST actions; COST 238, 251 and 271 (e.g. Zolesi et al., 2007; Zolesi and Cander, 2008). This joint work started on the early nineties and ever since then this community has worked hard to create a large and homogeneous ionospheric data base. The data base has continuously increased and has mainly been fed by data deduced from the ionograms obtained by vertical incidence (VI) soundings. The ionograms provide the critical frequen- cies and heights of the ionospheric layers over the measuring station and appropriate ionogram inversion tools provide the vertical electron density profiles. The main reason for this data base is to make data standardized and available to the ionospheric community for their purpos- es, e.g. research, telecommunication applica- tions, etc. Therefore, having data available is of capital importance for our community and this task has continued in the COST 296 action. This section discusses the task carried out by the COST 296 community to archive ionospheric data. The main data bases dedicated to this task will also be presented. At present, the stations producing ionospheric data linked to the COST 296 com- munity keep information on their measurements and most of them make the measurements avail- able on their own websites. The links to those stations can be found at the COST 296 web site (http://www.cost296.rl.ac.uk/). In addition, these stations also provide data to Data Bases (DB) maintained by COST 296 members. Most of DB keeps the acquired historical data, these being in- creased by received real-time data. The real-time data of modern ionosondes is deduced by intelligent algorithms (Galkin et al., 2008a) providing the so called «auto-scaled da- ta». Though known, it is worth noting the im- portance of real-time data accessibility for monitoring, forecasting and nowcasting the state of the ionosphere. The COST Prompt Ionospheric Database at the Rutherford Appleton Laboratory (RAL), UK (http://www.wdc.rl.ac.uk/cgi-bin/digison- des/cost_database.pl) continues to receive, cat- Vol52,3,2009 20-09-2009 19:05 Pagina 222 223 Near Earth space plasma monitoring under COST 296 alogue and archive auto-scaled VI data on a re- al time basis from ionospheric sounders across Europe. This data set includes 11 contributing instru- ments in Europe, at Athens, Chilton, Dourbes, El Arenosillo, Juliusruh, Lycksele, Pruhonice, Rome, Ebro, Tromsø and Warsaw (Cander, 2008). The DIAS project (http://www.iono.noa.gr/DIAS/), a pan-European distributed information server pro- viding information on the ionospheric conditions over Europe, is supporting the real-time acquisi- tion and archiving of the ionospheric observations currently obtained from eight European ionospher- ic stations operating in Athens, Rome, Juliusruh, Chilton, Ebro, Pruhonice, Lycksele and El Arenosillo (Belehaki et al., 2005, 2006). The IN- GV (Istituto Nazionale di Geofisica e Vulcanolo- gia), Rome, carried out the eSWua project aimed to realize a hardware-software system for DB to standardize historical and real time observations for different instruments installed by the upper at- mosphere group of INGV (Romano et al., 2008). The eSWua DB related to the Rome digisonde and the 4 GISTM (GPS Ionospheric Scintillation and TEC Monitor) measurements. A dynamic website (www.eswua.ingv.it) has been opened to the com- munity for real time access to raw and processed data. The Space Research Centre (SRC) Poland constructed a DB for VI data with standard for- mat for ionospheric data exchange IIWG (http://rwc.cbk.waw.pl/iiwg) which is being dis- tributed via the International Space Environ- ment Service (ISES) network and archiving da- ta distributed worldwide. SRC also makes avail- able daily reviews on solar, magnetic and ionos- pheric activity also. The Center for Atmospher- ic Research of the University of Massachusetts at Lowell (UMLCAR) continued to archive in the DIDBase all digisonde data available in real time via Internet (http://umlcar.uml.edu/DID- Base/) including the European COST 296 net- work. UMLCAR has proposed a new XML- based ionosonde data exchange format allowing addition of measurement uncertainties to the da- ta user, thus making the ionosonde auto-scaled data acceptable to the modern assimilation mod- els based on the Kalman filter method, such as the Global Assimilation Ionospheric Model, GAIM, (Galkin et al., 2008b). All of the above DB handle groundbased ionospheric data, giv- ing information on the bottomside ionosphere. The German Aerospace Center (DLR) automat- ically retrieves and archives of ionospheric radio occultation measurements onboard CHAMP satellite, giving not only bottomside but also topside ionospheric information. Electron densi- ty profiles from CHAMP can be accessed via the new SWACI service (Jakowski et al., 2006) at http://w3swaci.dlr.de/. In addition to providing the real-time data, it is worth mentioning here the availability of da- ta validated by experts. This type of data has an added value compared to the auto-scaled data, with a double application: they serve for testing the auto-scaling algorithms and a continuous feedback makes possible improvements to the above algorithms and a trusted ionospheric monitoring for research and modeling purpos- es. Accordingly, the DIDBase archives edited ionogram data together with the autoscaled val- ues for some stations. The edited data files in- clude the name of the expert, and the DIDBase user can select the files with the «most trusted» editor. The Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN) makes available validated data of 14 ionospheric characteristics recorded with the ionosonde system «Parus» at Moscow (http://www.izmiran.ru/services/iweather/dai- ly). The eSWua DB provides the validated da- ta of ionospheric observatories at Rome and Gibilmanna, Italy. The aforementioned COST Prompt Ionos- pheric Database provides on-line validated data from the Chilton ionosonde station, UK with one hour resolution. Other individual ionospher- ic stations make available their edited data through their websites. The Ebro Observatory, Spain makes available a catalogue of their vali- dated data availability and a data request form (http://www.obsebre.es/php/ionosfera.php). Most of these data have a one hour resolution, but 15 minute sampling data is available from May 2004 date. There are also several cam- paigns at 5 minute sampling available also, these being performed for detailed analyses of ionospheric behavior under specific events (So- lar Eclipses, Satellite validation data, etc). Vol52,3,2009 20-09-2009 19:05 Pagina 223 224 D. Altadill, J. Boska, L.R. Cander, T. Gulyaeva, B.W. Reinisch, V. Romano, A. Krankowski, J. Bremer, A. Belehaki, I. Stanislawska, N. Jakowski and C. Scotto 3. Validation of monitoring data Most of the research and work carried out in the past by the ionospheric community have been done using historical data validated by ex- perts. The current situation has significantly changed mainly due to the facilities of the in- formation society. A large amount of data is now available in real-time providing products to users soon after the data have been produced. However, the real-time data and related prod- ucts should contain warnings to users noting their quality and consistency. This section dis- cusses the task carried out by the COST 296 community to validate the quality and consis- tency of monitoring data and products, particu- larly those collected in real time. A large amount of ionospheric data pro- duced and used by the COST 296 community has been recorded by VI sounders, in particular the Digisondes built by the UMLCAR (http://ulcar.uml.edu/digisonde.html). This sys- tem is supplied with software of automatic scal- ing of ionograms (ARTIST), providing ionos- pheric data in quasi-real time. Sometimes, how- ever, the autoscaled data are not good enough and data users should be warned. A significant effort has been made to improve the autoscaled data by the ARTIST software (Galkin et al., 2008a) and uncertainties of the data have been added for user information. This has been done in part thanks to efforts of the experts validating data and subsequent comparisons and statistics. Though validated data are recommended for re- search purposes and for monitoring fine details of the ionospheric structure, most monitoring ionosonde stations now rely on automatic pro- cessing rather than edited processing to provide ionospheric characteristics. A systematic as- sessment of the quality of all the key ionospher- ic characteristics scaled automatically was made from hourly ionograms from the midlati- tude Chilton ionosonde in the United Kingdom, by comparing them with the definitive values produced by manual scaling (Bamford et al., 2008). The above comparisons clearly showed the improvement the goodness of the autoscal- ing software from the late 1990s to date (fig.1). Fig. 1. Time evolution of the correlation coefficients calculated for years 1996-2004 between manually scaled and autoscaled values of the indicated ionospheric characteristics. Results are obtained for Chilton station. Adapted from Bamford et al. (2008). Vol52,3,2009 20-09-2009 19:05 Pagina 224 225 Near Earth space plasma monitoring under COST 296 The investigation has been the first compre- hensive examination of the performance of au- tomatic scaling without any data pre-selection over an extended period covering the majority of solar cycle 23. The accuracy of autoscaled values during storm periods was examined against the global storm index Dst for the whole 9-year data set. Geomagnetic conditions were found to have only a small effect on autoscaling performance, with the most important identifi- able cause of error being the truncation of auto- matic layer traces due to broadcast interference. Overall, the performance of the autoscaling al- gorithms was found to be acceptable, with the characteristics foF2, h’E, M(3000)F2, and MUF(3000)F2 within defined error bounds for more than 90% of the time and all characteris- tics within these bounds more than 80% of the time. Also, the performance of the ARTIST al- gorithm used in digisondes for N(h) profiles and Doppler system measurements (common volume measurements) were tested for Pruhon- ice station (Buresova et al., 2007). It was found there that the results of ARTIST, as for height determination in N(h)-profiles, are essentially of good quality and reliable under quiet geo- magnetic conditions and in the absence of the sporadic-E layer, but rather unreliable during moderate and strong geomagnetic storms or in the presence of a well-developed sporadic-E layer. The discrepancies could be related to the uncertainties of the observational inputs and to the interpretation of the digisonde data. The groundbased data generated by digison- des served for calibration and validation of space-borne sensors, as the GUVI instrument onboard the TIMED spacecraft (DeMajistre et al., 2007) and CALVAL campaign for UV sensor onboard DMSP F-16 spacecraft and COSMIC constellation Radio Occultation profiles. The CVALVAL was supported by the real-time work of 34 digisondes (10 of them located in Europe). The COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) cam- paign in December 2006 was supported by 41 digisondes around the globe collecting electron density profiles at a 5-min cadence, including nine of the European COST stations. In addition to the above, the COST 296 community contributed to testing and validat- ing other data and techniques. The changing state of the ionosphere is generally monitored by networks of vertical ionosondes that provide us with regular ionospheric sounding. Many ionospheric applications require determination of the true-height electron density profiles N(h). Therefore, ionograms must be further in- verted into N(h). The consistency of two differ- ent methods of obtaining electron density pro- files from inversion of ionograms POLAN (Titheridge, 1985) and NHPC (Huang and Reinish, 1996; Reinish et al., 2005), widely used by the ionospheric research community was analyzed. The analyses were carried out for two midlatitude ionospheric stations (Sauli et al., 2007) and the results show significant sys- tematic differences between N(h) calculated by these two inversion methods. NHPC provides smoother time variation than POLAN does. POLAN systematically obtains heights lower than NHPC for nighttime profiles, the opposite being true for daytime profiles. The best agree- ment of these two methods is seen for two-lay- er profiles. Location of the largest difference between profiles corresponds to the F1 region and transition region between F1 and F2 re- gions. The results are consistent at two distant observatories and they remain the same through changing solar and geomagnetic activity. As the validation of vTEC maps refers, the accuracy of the European RAL vTEC maps un- der stormy conditions of 17-21 January 2005 were assessed by applying the tests used to val- idate the International GNSS Service (IGS) vTEC (Orus et al., 2007). The results show dis- crepancies between the RAL vTEC and IGS maps which lead to significant RMS and bias values regarding to the self-consistency and al- timeter test of several TEC units during storm conditions. A Kriging technique applied in this work gave a relative improvement up to 26% in the highest storm conditions. 4. Development of ionospheric monitoring techniques and parameters The main monitoring techniques and pa- rameters describing the state of the ionospheric plasma developed by the COST 296 communi- Vol52,3,2009 20-09-2009 19:05 Pagina 225 226 D. Altadill, J. Boska, L.R. Cander, T. Gulyaeva, B.W. Reinisch, V. Romano, A. Krankowski, J. Bremer, A. Belehaki, I. Stanislawska, N. Jakowski and C. Scotto ty, including ground-based and space based techniques, are discussed in this section. The variability of the critical frequency of the F2 layer, foF2, over ionospheric station Grocka (44.48°N, 20.31°E) was studied during the declining phase of the solar cycle 23 from 2004 to 2006 (Mitic and Cander, 2008). The variability index was introduced to identify the daily and seasonal patterns characterizing the local mid-latitude ionosphere during quiet and disturbed geomagnetic conditions. In addition, the behavior of the vTEC values, obtained from GPS measurements in the surrounding area un- der these conditions is reported. The analysis shows a number of interesting features repre- sentative of the ionospheric variability relevant for ionospheric modeling as well as ionospher- ic propagation applications based on a single station approach. An ionospheric activity index was developed in the DIAS project co-funded by the eContent program of the European Union (Belehaki et al., 2005). It proposed a new ionospheric activity in- dex derived from automatically scaled online data from several European ionosonde stations (Bremer et al., 2006). The index describes the ionospheric disturbance level at different Euro- pean ionosonde stations and it is derived on-line from automatically scaled ionosonde observa- tions. These indices are used to distinguish be- tween normal ionospheric conditions expected from prevailing solar activity and ionospheric disturbances caused by specific solar and atmos- pheric events (flares, coronal mass ejections, at- mospheric waves, etc.). The most reliable in- dices are derived from the maximum electron density of the ionospheric F2-layer expressed by the maximum critical frequency foF2. Simi- lar indices derived from ionospheric M(3000)F2 values show a markedly lower variability indi- cating that the changes in altitude of the F2-lay- er maximum are proportionally smaller than those estimated from the maximum electron density in the F2-layer. By using the ionospher- ic activity indices for several stations the ionos- pheric disturbance level over a substantial part of Europe (34°N-60°N; 5°W-40°E) can now be displayed online. A planetary index of the ionospheric changes does not exist so far because it can be difficult to immediately deduce it from a mix- ture of increases and decreases of plasma den- sity and electron content on the globe. This task is resolved using the numerical GPS-IONEX maps of the vTEC, available daily since 1998 (Gulyaeva and Stanislawska, 2008). The vTEC values are extracted at 600 grid points of the map at latitudes 60ºN to 60ºS with a step of 5º and longitudes 0º to 345ºE with a step of 15º providing hourly values for 0 to 23 h of local time for a representative set of conditions dur- ing a period 1999-2008. The local effects of so- lar radiative energy are filtered out. The deriva- tion of the planetary perturbation index is a two-step process. The first step consists of generating a W-in- dex map, a degree of perturbation computed as the logarithm of vTEC relative to quiet refer- ence taken as daily-hourly median for 27 days prior the day of observation. The planetary Wp index is obtained in the second step from the above W-index map as the latitudinal average of the ranges between maximum positive index and minimum negative index which are weight- ed by the latitude-longitude extent of the ex- treme index values on the map. The single-sign Wp index varies from 2 to 16 units providing the solar cycle variation of the planetary ionos- pheric storms. The Wp index shows equinoctial maxima, these being correlated with the Dst in- dex. The planetary Wp index discloses the dis- turbances which may belong either to magne- tosphere or the ionosphere-plasmasphere sys- tem or both providing broader proxy index driv- ing the space weather than the geomagnetic in- dices alone. Instantaneous mapping techniques have been applied to monitor European, Asian and Japanese region as well as a 24 hours ahead forecast for the above regions and at some ionospheric stations (Stanislawska et al., 2000). The INGV has developed a computer pro- gram (Autoscala) for the automatic scaling of the critical frequency foF2 and MUF(3000)F2 from ionograms (Pezzopane and Scotto, 2007) that has been extended for obtaining the spo- radic-E layer (Scotto and Pezzopane, 2007) and the F1 layer (Pezzopane and Scotto, 2008). Au- toscala was designed to scale automatically the ionospheric parameters from the ionograms Vol52,3,2009 20-09-2009 19:05 Pagina 226 227 Near Earth space plasma monitoring under COST 296 recorded by the AIS (Advanced Ionospheric Sounder) developed at the INGV but it can be easily applied to scale the ionograms obtained by any kind of ionosonde. The INGV has re- cently developed the above software related to the AIS with a routine for the real time compu- tation of the electron density profile, which is essential for space weather applications. The electron density profile is computed with a model (called Adaptive Ionospheric Profiler, AIP) with 12 free parameters (6 related to the E-region and 6 to F2-F1 layers). The parame- ters defining the profile are initially estimated considering the helio-geophysical conditions and the ionospheric characteristics obtained au- tomatically from the ionograms by Autoscala. Then the candidate profile is inverted into trace and is adapted to a final computed profile by minimizing the root mean square error between the trace restored from the candidate profile and the recorded one. The model is capable of de- scribing a wide set of ionospheric profiles and the related research has been accepted for pub- lication in Advances in Space Research. The Standard DDA method of drift velocity evaluation (Reinisch et al., 2005) has been im- proved by skymap-points selection in three steps as a quality control and improvement (Kouba et al., 2008): (i) robust height range se- lection, (ii) setting limits on Doppler frequency shift, and (iii) setting limits on the echo arrival angle. Such approach requires a sufficiently large amount of data points in skymap. Raw drift data from Pruhonice observatory for peri- od Jan-May 2006 were recalculated using this method. Preliminary results show the behavior of the F-region drift: velocity components diur- nal variability during quiet geomagnetic condi- tions and seasonal trends of daily characteris- tics. As significant decrease in the daily-maxi- mal horizontal component from winter to sum- mer 2006 was found within the analyzed data. This method excludes multiple and/or too oblique reflections. The above method enables E-region and F-region drifts to be separated (this is not routinely done by any other ionos- pheric sounding station), characteristics of which are substantially different. Since May 2005, the Pruhonice Digisonde measures E-re- gion drifts every 15 minutes, using four fixed frequencies between 2.0 and 2.6 MHz. Unlike the autodrift setting, E-region sounding fre- quencies do not depend on critical frequency, they are set and fixed for all measurements. During summer 2006 the first special campaign for monitoring drifts in Es-layer was per- formed. Drift-measurement on a higher sound- ing-frequency window 3.2-4.7 MHz was run every 15 minutes in addition to the standard E- region drift measurement. E-region drift meas- urement with a two frequency-window setting represents an important source of information on the dynamics of the E-region ionosphere and brings new pieces of information on sporadic E layer formation and its behavior. Differences of the plasma motion confirm the different dy- namics of E and Es layers. The new phase-difference technique for Digisondes was evaluated for monitoring pre- cise heights records of ionospheric layers. The program settings for this technique were pro- vided by the UMLCAR. The technique, which analyzes the phase differences between signals at slightly different frequencies, allows meas- urement of the reflection range, i.e., the virtual height h’(f) for vertical sounding, with accura- cies better than one kilometer (Reinisch et al., 2008). First results of measurements carried out at Millstone Hill demonstrate the robustness and reliability of the developed technique, and show the potential of the method for routine ap- plication. The technique has been applied in a specific campaign of precise measurements of virtual height of the E-layer carried out under the International Heliophysical Year (IHY) ini- tiatives of the COST 296 whose preliminary re- sults will be discussed later. The mapping techniques developed by Krankowski et al. (2007) provide regular vTEC monitoring over Europe. The vTEC maps are created from GPS observations collected at IGS and EUREF Permanent Network (EPN). The large number of stations in Europe provides good data coverage yelds high-accuracy vTEC maps with an error at a level of 1-3 TEC units. The vTEC maps are available with a spatial res- olution of 100-300 km and a time resolution of 5 minutes. Figure 2 shows examples of the above TEC mapping technique above European area for particular time intervals. Vol52,3,2009 20-09-2009 19:05 Pagina 227 228 D. Altadill, J. Boska, L.R. Cander, T. Gulyaeva, B.W. Reinisch, V. Romano, A. Krankowski, J. Bremer, A. Belehaki, I. Stanislawska, N. Jakowski and C. Scotto 5. Dissemination of data and products Most of the above ionospheric data and products have been set on-line and disseminat- ed to the e research community and users. As already mentioned above, most institutions par- ticipating in the COST 296 action have their own websites making available their data and products. This section highlights, the main tasks carried out by the COST 296 community to support and develop internet sites and proto- cols for disseminating data products. The Space Weather Web Facilities for Radio Communications Users of the RAL has contin- ued to maintain, support and improve (http://ionosphere.rcru.rl.ac.uk/). This facility is based on the contributions of a number of COST 296 participating institutions and it is 24/7 on-line service that includes the following products: (1) Interactive forecast maps of foF2, MUF(3000)F2 and ITU-R NeQuick modelled TEC values over Europe based on ionosonde measurements. (2) Near real-time dynamic sys- tem for monitoring ionospheric propagation conditions over Europe. (3) Near real-time TEC maps over Europe and 24 hours single station plots based on TEC evaluation from IGS GPS measurements. (4) Near real-time solar-terres- trial and ionospheric indices and warning mes- sages so that ionospheric and trans-ionospheric propagation conditions are known to worldwide users. (5) Archive of all data and images. The service has also been extended to enable users to extract ionospheric profiles from Standard Archive Output files (SAO) as calculated by the NHPC algorithm applied by UMLCAR digisondes, in addition to those calculated by POLAN. The server at Regional Warning Centre (RWC) of the SRC, Poland, fed with URSIGRAMS of COST 296 stations and others provides some ionospheric characteristics in quasi-real time and from the previous 2 months (http://cbk.waw.pl/rwc and ftp://www.cbk.waw.pl/idce/). In addition, it provides 24 hours ahead fore- cast maps of ionospheric characteristics for Eu- ropean, East Asia and Australia regions and the forecast of some ionospheric characteristics for individual stations. In particular, the Web serv- ices of the Ionospheric Dispatch Centre in Eu- Fig. 2. The detailed TEC maps over Europe with 5-minute resolution during the eclipse day on 3 October 2005 (a) and one day after the solar eclipse on 4 October 2005. Vol52,3,2009 20-09-2009 19:05 Pagina 228 229 Near Earth space plasma monitoring under COST 296 rope (SRC) provide on line access to data base of the critical frequency of F2 ionospheric lay- er and M(3000)F2 forecast for all available sites. The ionosonde data are available from 1983 up to the latest measurements from all over the world in IIWG format. The GPS meas- urements from Warsaw station are also avail- able. Daily plots for 30 stations from all over the world are presented along with their digital version. It also makes available daily reviews on solar, magnetic and ionospheric activity. Catalogues of the quiet and disturbed days and of ionospheric disturbed periods lasting three hours or longer are compiled and presented for European stations (these catalogues are avail- able at the IZMIRAN Web site also). Finally, the links to the websites of COST 296 related topics are available on the web navigator (http://rwc.cbk.waw. pl/cost296/ ). The IZMIRAN team has set up a website on ionospheric weather (http://www.izmiran.ru/serv- ices/iweather/). Data of 30 ionospheric stations (foF2, hmF2 and their deliverables) are presented therein for the current month. The past data are available in the archive for two years proceding the current month. Missed data are reconstructed by cloning data of other stations so the data sets are complete for the daily-hourly grids (Gulyaeva et al., 2008). The ionospheric disturbances are be- ing indexed in comparison with the running medi- an of the preceding 27 days calibrated with ITU- R prediction of the seasonal trend. A proxy for foF2 critical frequency has been created by apply- ing a technique for reducing the foF2 critical fre- quency as a function of the solar zenith angle (Gulyaeva, 2009). The technique improves the correlation between the data of different stations and the inter-seasonal correlations at a given loca- tion, and it is applied for reconstruction of missed observations of foF2 at 30 stations worldwide, thereby increasing the number of stations data at the Ionospheric Weather web site, including some stations at low and high latitudes in both North and South Hemispheres. A dynamic website has been opened to the community for real time access to raw and processed data within the eSWua project of the INGV (www.eswua.ingv.it), also reported in Section 2. The site is based on measurements performed by all the instruments installed by the upper atmosphere group of INGV (Romano et al., 2008). This interactive website supports a well organized data base aiming to be a power- ful tool for the scientific and technological com- munity in the field of telecommunications and Space Weather. The eSWua is contributing to the projects in the frame of international collab- orations where the interoperability of the system and effective data access are necessary require- ments (Virtual Observatories, www.egy.org, and Interhemispheric Conjugacy Effects in Solar- Terrestrial and Aeronomy Research, ICESTAR, http://www.scar-icestar.org). The eSWua allows the user to explore and download validated ver- tical sounding data since 1976, view the iono- grams and access the automatic scaled data. Specific tools to survey the ionospheric behav- iour both for real and historic time have been de- veloped and are already accessible by web. 6. COST 296 campaigns Using the potential of the different observ- ing and monitoring systems belonging to the participating institutions in COST 296, two campaigns have been carried out, a campaign to follow ionospheric effects of the annular eclipse occurred over Europe on 3 October 2005 and a campaign contributing to the objec- tives of the third CAWSES Global Tidal cam- paign from 1 June to 14 August 2007. On the occasion of the annular eclipse, which occurred over Europe in the morning hours of 3 October 2005, the COST 296 com- munity prepared a specific campaign for moni- toring its effects on the ionosphere to obtain a comprehensive view of the eclipse by utilizing different observation techniques. The well-de- fined obscuration function of solar radiation during the eclipse provided a good opportunity to study the ionospheric/thermospheric re- sponse to solar radiation changes during the eclipse (Jakowski et al., 2008). Since the peak electron density behavior of the ionospheric F2 layer follows the local balance of plasma pro- duction, loss and transport, the ionospheric plasma redistribution processes significantly af- fect the shape of the electron density profile. These processes have been discussed based on Vol52,3,2009 20-09-2009 19:05 Pagina 229 230 D. Altadill, J. Boska, L.R. Cander, T. Gulyaeva, B.W. Reinisch, V. Romano, A. Krankowski, J. Bremer, A. Belehaki, I. Stanislawska, N. Jakowski and C. Scotto a comparison of vertical incidence sounding (VS) and vertical total electron content (TEC) data above-selected ionosonde stations in Eu- rope. The equivalent slab thickness, derived with a time resolution of 10 min, provides rela- tively good information on the variation of the electron density profile during the eclipse. The computations reveal an increased width of the ionosphere around the maximum phase (fig. 3). As indicated by the available measurements over Spain, the photo production is significant- ly reduced during the event leading to a slower increase in the total ionization in comparison with the neighboring days. The supersonic mo- tion of the Moon’s cool shadow through the at- mosphere possibly generated atmospheric waves that were detected at ionospheric heights above the Spanish station (fig. 4). High-fre- quency (HF) Doppler shift spectrograms were recorded during the eclipse showing a distinct disturbance along the eclipse path. Although ionosonde and HF Doppler measurements show enhanced wave activity, the TEC data analysis does not, which is an indication that the wave amplitudes are too small for detecting them via this interpolation method. More about wave ac- tivity is in Bremer et al. (this issue). The total ionization decreases up to about 30% during the event. A comparison with similar observations from the total solar eclipse of 11 August 1999 revealed a remarkably different ionospheric be- havior at different latitudes. A detailed analysis based on GPS observa- tions from EUREF were used to observe the response of TEC (Total Electron Content) to the total solar eclipse on October 3, 2005 (Krankowski et al., 2008). The effect of the eclipse was detected in diurnal variations and more distinctly in the variations of TEC along individual satellite passes. The trough-like variations with a gradual decrease and fol- lowed by an increase in TEC at the time of the eclipse were observed over a large region. The depression of TEC amounted to 3-4 TECU. The maximum depression was observed over all stations located at the maximum path of the Fig. 3. Variations of the ionospheric slab-thickness over the Ebro, Spain (left) and Juliusruh, Germany (right) stations during the solar eclipse on 3 October 2005. After Jakowski et al. (2008). Vol52,3,2009 20-09-2009 19:05 Pagina 230 231 Near Earth space plasma monitoring under COST 296 solar eclipse. The delay of a minimum level of TEC with respect to the maximum phase of the eclipse was about 20-30 min. The two-di- mensional TEC maps constructed with high temporal resolution (5-min interval) show that the eclipse produced remarkable changes in the structure of the ionosphere. These TEC maps demonstrate also that the depression of TEC reached 20-30% compared to a quiet day (October 4, 2005). The COST 296 community had performed a coordinated E-Layer Precision Group Height Measurement (PGHM) campaign to contribute to the objectives of the Third CAWSES Global Tidal campaign run from 1 June to 14 August 2007. The campaign was based on the advan- tage of High Doppler resolution mode tech- nique embedded in the Digisondes which makes able to measure the virtual heights h’(f) of the E-layer with an accuracy better than 1 km (Reinisch et al., 2008). Eight European ionospheric stations participated to this initia- tive; Tromso (69.6°N, 19.2°E), Juliusruh (54.6°N, 13.4°E), Chilton (51.6°N, 358.7°E), Pruhonice (50.0°N, 14.6°E), Rome (41.8°N, 12.5°E), Ebro (40.8°N, 0.5°E), Athens (38.0°N, 23.6°E), and Arenosillo (37.1°N, 353.3°E). Ebro and Arenosillo had stopped the campaign on July 14 due to noisy and unreli- able measurements. Athens and Rome record- ed good nighttime data, making possible analy- ses for nighttime sporadic E-layer height changes. The other stations recorded high qual- ity measurements clearly showing the two dif- ferent regimes for nighttime and daytime E- layer height variations. An example of the campaign measurements recorded at Chilton station is depicted in fig. 5. A number of interesting effects on the daily variations of the E-region virtual heights were observed: day-to-day variability of the E-region heights, repetitive «hooks» in the height records (inter-diurnal variations) and a distinct diurnal variation. Preliminary ideas on the observed ef- fects suggest that day-to-day variability of the E-region height variations could be related to planetary wave modulation of metallic ion transport while inter-diurnal variations may be caused by tidal/gravity wave activity in that re- gion. Although not shown here, spectral analy- sis revealed other interesting phenomena: sta- tion-to-station variations in the diurnal harmon- Fig. 4. Contour of the electron density above Ebro station, Spain as function of time and height for October 3, 2005. Note the train of height oscillations starting at about 08:00 UT and further developed from 10:00 to 14:00 UT. After Jakowski et al. (2008). Vol52,3,2009 20-09-2009 19:05 Pagina 231 232 D. Altadill, J. Boska, L.R. Cander, T. Gulyaeva, B.W. Reinisch, V. Romano, A. Krankowski, J. Bremer, A. Belehaki, I. Stanislawska, N. Jakowski and C. Scotto ics (24, 12, 8 hours), and possible evidence for the coupling of tidal (24 h) and long period os- cillations (120 h). Results of the data analysis demonstrated great potential offered by the ionospheric sounding with enhanced range res- olution. Though results presented are focused on the E-region, the technique may be applied to other ionospheric regions. 7. Summary and concluding remarks The main achievements of the near Earth space plasma monitoring under COST 296 may be summarized as follows. The historical and real-time data bases of the soundings of the ion- osphere have been maintained and increased with continuous flowing of monitoring data. The COST 296 community succeeded in mak- ing data standardized and available to the ionos- pheric community for their purposes as re- search, modeling and telecommunication appli- cations, this being possible throughout the web- sites of the stations managed by COST 296 par- ticipants. Many validated data have also been made available. The added value of the validat- ed data served for testing the auto-scaling algo- rithms and a continuous feedback makes possi- ble improvements to the above algorithms, and a trusted ionospheric monitoring for research and modeling purposes. The quality of the real- time data quality was systematically assessed for key ionospheric parameters, serving to pro- vide data users measurement uncertainties and Fig. 5. E-region precision group height measurements at Chilton, UK as function of time for June 2007. The horizontal axes represent time (Universal Time) and the vertical axes represent virtual height (km). The grey shaded areas indicate night-time measurements and the arrows point out significant inter-diurnal height varia- tions as hook shaped or trains of height oscillations. Vol52,3,2009 20-09-2009 19:05 Pagina 232 233 Near Earth space plasma monitoring under COST 296 to improve automatic scaling algorithms, and so making the real-time data acceptable to modern assimilation models. The availability of the ed- ited data also served for calibration and valida- tion of space-borne sensors. Moreover, a tech- nique for improving the discrepancies of differ- ent mapping services under stormy conditions has been developed. Further techniques and pa- rameters have been developed for monitoring the near Earth space plasma. Time dependent 2D maps of TEC and key ionospheric parameters are available on-line throughout the websites of the COST 296 par- ticipants and activity indices for distinguishing disturbed ionospheric conditions have been ob- tained for real-time applications. Most of the above achievements have been obtained for ground VI data or for vTEC derived from GNSS signals. The potential of the different ob- serving systems for ionospheric monitoring has been combined to obtain a comprehensive view of the effects of a solar eclipse on the iono- sphere. Thanks to the cooperation for the last 4 years in the frame of the COST 296 action, sig- nificant progress has been achieved for data availability and validation, 2D monitoring products, and dissemination of products. How- ever, a step forward is needed in the future, es- pecially to combine different ionospheric ob- serving systems for monitoring. The develop- ment of 4D techniques of ionospheric monitor- ing (time dependent 3D products) would be the goal of further cooperation actions. 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