LCDA. ALEIDA CENTENO RODRIGUEZ

2.1 History 

2.2 Future: Transformational Science Enabled by the AGCP-UAF

3. Existing and Planned Argentine Support

3.1 Potential Locations for UAF-AGCP

4. Steps Toward a AGCP-UAF

5. AGCP Workshop Concluding Statement

6. References

7. Acknowledgements

Appendix: AGCP Workshop Organization and Participation

1. Overview

In recent years, it has become increasingly clear that the Earth is fully engulfed in the tenuous outer envelope of the solar atmosphere thereby causally coupling solar atmospheric phenomena to the Earth’s atmosphere-ionosphere-magnetosphere (A-I-M) system. The resultant magneto-ionic plasma effects on the A-I-M system, and their source functions, are global phenomena that require for their study utilization of global arrays of instruments. This point was highlighted in the 2002 National Research Council report The Sun to Earth and Beyond: A Decadal Research Strategy in Solar and Space Physics1. It is this realization also that brought together an international community of researchers at a workshop sponsored by the National Astronomy and Ionosphere Center (NAIC) Arecibo Observatory in April 2006 to assess future research requirements for facilities that will enable study of these phenomena.Global instrument arrays with high angular and temporal resolution are needed to enable us to monitor the atmosphere as a whole with sufficient resolution to resolve mesoscale phenomena and to follow their dynamical evolution. Extended coverage in longitude as well as latitude is needed to obtain tidal phases and to study effects that are dependent upon magnetic declination. The necessity for global coverage has its origin in the fact that each latitudinal region has its own physical character. For example, the dynamical and electromagnetic processes in the auroral zone have a very different physical character than those occurring at equatorial latitudes.

   Understanding energy transfer between different latitudinal regions is crucial for accurate prediction of the ionospheric response to Space Weather. It is also a very challenging problem. Similarly challenging is the quest to understand the energy transfer from below to above via gravity, tidal and planetary waves. The three dimensional structure of A-I-M coupling throughout a global phenomenon means that in addition to a global array of diagnostic instruments, we also need to employ specific instruments at several sites worldwide that are designed to probe the atmosphere, ionosphere and magnetosphere at different heights. While difficult, the 3-D problems are amendable to investigation by a well-planned, global, array of instruments. The requirements are spelled out in the comprehensive NRC decade strategy report.

   The participants at the April 2006 international workshop established their primary goal as that of addressing the deficiency of research instruments in the southern hemisphere. This deficiency is currently the major barrier restricting truly global studies. Secondarily, the workshop participants emphasized the need to leverage the superb research capabilities at the Arecibo Observatory for the study of the 3-dimensional structure of the A-I-M system, particularly for those phenomena tied to the geomagnetic field. There was unanimous agreement that this latter goal can be achieved most effectively by establishing a new research facility, including an ISR complement to the Arecibo radar, at the southern hemisphere Arecibo geomagnetic conjugate point (AGCP). The AGCP is located in Argentina.  The task of finding options for an ISR complement to the 305-m Arecibo telescope is a considerable one.

   Fortunately, over the last decade the NSF has funded the development of the Advanced Modular Incoherent Scatter Radar (AMISR), a solid-state synthetic aperture radar of high power and great operational flexibility. AMISR is being installed in a one-face configuration in Poker Flat, Alaska. It has begun commissioning tests with the goal of becoming fully operational before the end of 2006. This radar was purposefully designed to be relocatable, in whole or in part, to a new geographical location of special interest to the Aeronomy and Space Science community. AMISR is an ideal ISR complement to the Arecibo ISR for a AGCP facility. As outlined in the Coupling Energetic and Dynamics of Atmospheric Regions (CEDAR) meeting held in Santa Fe, NM in June of 2005, NSF soon will be calling for suggestions from the community on future sites where AMISR could be moved or additional AMISR sites established. As scientist-members of the U.S. and international ionospheric communities, the workshop participants recognized that placing an AMISR face in Argentina near or at the AGCP represents a unique research opportunity. Together with the Arecibo ISR, it will enable simultaneous studies in the northern and southern hemispheres of a wide range of geophysical phenomena causally related to the vertical structure of same geomagnetic field lines, north and south. This realization, and the specific plan of combining the capabilities of Arecibo with AMISR at the AGCP was the highlight of the international community workshop.

   At the workshop, a wide variety of scientific questions with large impact in the Space Weather and Aeronomy field were identified that are amenable to being answered by the establishment of an upper atmospheric facility (UAF) at the AGCP (hereafter referred to as UAF-AGCP). The Workshop participants recognized that the successful installation and operation of international science facilities have been possible in the past with collaboration between U.S. and international scientific institutions. We seek to build on this experience. Such collaboration also offers additional benefits through apolitical intellectual and cultural exchange as well as educational opportunities in Space Science, Computer Science, Engineering and Mathematics that we wish to exploit for the benefit of U.S. and Argentine students. Finally, we recognize that it is now possible to construct a very cost-effective ISR, at low-risk, thanks to the development of AMISR by the NSF. In this report we present a summary of the scientific, technical and strategic discussions addressed during the Workshop, results from additional studies, and an outline of a series of recommendations to achieve the goal of creating an UAFAGCP.

2. Science Opportunities and Objectives with an Arecibo Geomagnetic Conjugate Facility

2.1 History

   The idea and need for conjugate magnetic studies using paired ISR instruments on each end of the magnetic field line, north and south, originated soon after the Arecibo 430 MHz radar was operational in the early 1960’s. Carlson (1967a;b) observed enhancements of the O(1D) 6300 and N2+ 3914 lines by conjugate photoelectrons. Behnke (1970) noted that the nighttime F region polarization E-fields at Arecibo depended on the polarization fields at both Arecibo and the conjugate point. Cogger and Nelson (1971) associated the timing of similar airglow enhancements and the early morning ascent of the local F-layer ionosphere with the onset of conjugate photoelectrons. Later in the 1980’s, Burnside et al. (1983) began a series of thermospheric neutral wind observations by measuring the Doppler shifts of O(1D) emissions with a Fabry-Perot interferometer. Most of the time, the neutral winds and ion drifts, observed with the Arecibo ISR are coupled and move together.

   However, during conjugate sunrise in winter the local ionosphere also may be affected by polarization electric fields that are mapped to Arecibo’s latitude along the common magnetic field line. When this happens, the ion-neutral coupling may break down; the ions drift and separate along different paths away from the neutrals. Burnside et al. gave observational support to this idea with conductivity measurements obtained from Arecibo and, simultaneously, from a station near Arecibo’s magnetic conjugate point which at that time was located near Puerto Argentino, Malvinas, Argentina.

   Burnside and his collaborators observed that when the wintertime conductivities of the southern hemisphere exceeded those at northern latitudes, the electric fields from the conjugate ionosphere dominate those at Arecibo, and thus have a greater influence on the motion of the ions. Walker (1988) also pointed out the importance of the conjugate ionosphere to the complete understanding of Arecibo electrodynamics by reporting surprisingly large height variations for the F-region peaks in Arecibo radar observations of electron density profiles. While these variations are possibly the result of changes in the meridional wind speed and direction induced by the tidal structure and traveling ionospheric disturbances, Walker also noted that there is a third mechanism acting that will induce such changes, viz., a zonal gradient in the F-region current. Such changes may be driven by the E-region dynamics and the global electrodynamics. Model simulations clearly demonstrated the need to include the conjugate ionosphere—without including the conjugate ionosphere, the zonal current could not be conserved. A simplified model, including the conjugate ionosphere, gives realistic results near the F-region peak, and shows that the F-region peak can adjust itself upward or downward depending upon how the gradient of the eastward current changed.

   Examination of Arecibo radar and optical data on F-region ion drifts, and of thermospheric neutral winds, showed that while there is not likely to be much meridional current, the lack of a strong correlation between the zonal neutral wind and the zonal plasma drift suggests that there must be an eastward current. The model also demonstrated that the variations in the F-region peak height can be reproduced by changing the magnitude of the zonal current gradient (i.e., allowing for a local divergence in current). This then raises a very sticky problem: namely, how can the current be conserved given that there is a divergence in the zonal current? Creatively, Walker suggested that in the conjugate hemisphere there exists a gradient in the zonal current that opposes the direction of the current gradient in the local ionosphere. This would suggest that the F-region heights (and plasma density) of the local ionosphere and the conjugate ionosphere would be anti-correlated. This can be tested directly.

   Finally, it has been observed in 1997 ionospheric heating experiments at the Arecibo Observatorythat HF heater can create large plasma sheets within the meridional planesand yield large-scale plasma turbulence (Lee et al., 1998 a & b; Lee et al., 1999). When these plasma sheets had E x B drifts, they were detected by the Arecibo 430 MHz radar and seen as slanted stripes in the range-time-intensity (RTI) plots (see Figure 1). It has been demonstrated that NAU-generated signals at 28.5 kHz can be favorably guided by these HF heaterinduced plasma sheets (acting as parallel-plate waveguides), to propagate from Puerto Rico coherently all the way to the Arecibo geomagnetic conjugate point now near Puerto Madryn, Argentina, in the form of ducted whistler waves (Starks and Lee, 2000; Starks et al., 2001). Such conjugate experiments provide extremely effective probes of ionospheric plasmas and radiation belts, and yield crucial information on wave-plasma and wave-particle interactions.

2.2 Future: Transformational Science Enabled by the AGCP-UAF

After more than 4 decades of successful, transformational, science done at Arecibo, many of the most fundamental questions of ionospheric physics still remain unanswered. It is now apparent that they can only be successfully addressed with an Upper Atmospheric Facility at the Arecibo Geomagnetic Conjugate Point. As reflected in the rich scientific agenda presented at the workshop (see Appendix A) the research opportunities that will be realized by developing an UAF-AGCP located near the coast of Argentina are numerous. All these opportunities are of unique importance in guiding us to understand the dynamics and structure of the ionosphere and to obtain the necessary parameters to create precise models. At Arecibo, we know that there are very large gradients in density, as well as all kinds of structures at “sub-grid” resolution in global models. The Arecibo ISR limited “coning” motion prevents the gradients to be monitored adequately. With an AMISR suitably placed near the conjugate point having a much larger field of view, it will be possible to observe the ion velocity distributions over an extremely large region of sky and, in so doing, unravel the physical processes involved.

   Experiments performed at Arecibo in December 2005 during evening periods give evidence for conjugate photoelectrons precipitating through the field lines. The experiments were performed during this particular time of day to understand the effect of conjugate photoelectrons on the gyro line in the ISR spectra. The results, surprisingly, showed the reappearance of the plasma line after astronomical twilight at Arecibo, that could only be attributed to conjugate photoelectrons. The results also indicated that the F-region gyro line gets enhanced in the presence of the same conjugate photoelectrons (Figure 2). These results lead to the conclusion that there is a definite wave-particle interaction process going on during the evening period that directs the conjugate photoelectrons into the local ionosphere. However, we do not have any information about the conjugate ionosphere parameters such as electron density or temperature. These parameters are needed to enable us to understand these phenomena quantitatively. An AMISR face at the conjugate point of Arecibo would be the ideal instrument for this purpose. Whistler waves are electromagnetic plasma waves arising from the conversion of naturally occurring or man-made radio waves over a broad range of frequencies. Intense whistler waves can interact with the ionosphere and magnetosphere effectively, generating plasma modes and density irregularities, accelerating charged particles, and triggering electron precipitation. Controlled experiments on whistler wave propagation and interactions with ionospheric plasmas and radiation belts can be simultaneously conducted at the Arecibo

   Observatory in Puerto Rico and at the Arecibo geomagnetic conjugate point in Argentina. In recent Arecibo experiments evidence was found that NAU 40.75 kHz whistlers can excite lower hybrid waves to accelerate electrons effectively in the F-region and cause electron precipitation from radiation belts at L = 1.35. Displayed in Figure 3 is one set of data taken by Arecibo radar at 00:22:21, 00:22:31, and 00:22:41local time, respectively, with a 10-second integration time, on December 21, 2004, showing prominent plasma line enhancement in the nighttime F region, when the NAU transmitter was on, and spread F echoes were intense. Enhanced plasma lines occurred at 00:22:31 LT as displayed in the middle plots [denoted by (B) & (B’)]. They appeared at altitudes around 300 ±70 km, having a signal to noise ratio (SNR) of ~ 70. The frequency spectra of these enhanced plasma lines range from 3.5 to 5 MHz with a center frequency around 4.2 MHz. These characteristic features of plasma line enhancement can be reasonably understood by the following scenario. The NAU-generated 40.75 kHz whistlers are intense enough to excite lower hybrid waves and zerofrequency field-aligned plasma density irregularities in the ionospheric F region over Arecibo [Lee and Kuo, 1984]. These lower hybrid waves, generated in a broad range of altitudes at the wake of 40.75 kHz whistlers, have a single frequency of 40.75 kHz with a spectrum of wavelengths. They can effectively accelerate electrons continuously along the Earth’s magnetic field with energies from a fraction of 1 eV to 10 eV. These energetic streaming electrons, when detected by Arecibo 430 MHz radar, give rise to enhanced plasma lines with a frequency spectrum of ~ 3.25 – 4.75 MHz [see Figure 3-(B)].

   It has been found in Arecibo experiments conducted from December 27, 2005 to January 3, 2006 that the occurrence of nighttime E-region plasma line enhancement over Arecibo is closely correlated with the NAU transmissions at 40.75 kHz in Puerto Rico. Presented in Figure 4 is a set of typical data, that has three sequential frequency-altitude-intensity (FRI) plots of plasma lines measured at 03:31:48, 03:31:58, and 03:32:08 local time (LT), respectively, on December 31, 2005. The E-region plasma line enhancement refers to the spiky bursts seen in the middle plot, as an episodic, short period of phenomenon typically lasting for less than 10 seconds. These enhanced plasma lines having a signal-to-noise ratio (SNR) of 4-5 appeared at an altitude around 120 km, covering a range of ~ 40 km. The frequency spectra of enhanced plasma lines have a center frequency of 2.5 MHz with a bandwidth of 1.5 MHz. The aforementioned characteristic features of enhanced E-region plasma lines support the following scenario. NAU-generated 40.75 kHz whistlers interact with energetic electrons of ~ 0.5 MeV in radiation belts at L = 1.35, and subsequently cause electron precipitation into the lower ionosphere to ionize neutral particles with ionization energies of ~ 13 eV. The precipitated electrons stream along the Earth’s magnetic field, giving rise to enhanced E-region plasma lines with a center frequency of 2.5 MHz and a bandwidth of 1.5 MHz. This frequency spectrum corresponds to electron energies of 2.3 – 8.5 eV, which are in good agreement with the residual energies of those precipitated electrons from the radiation belts.

   The experimental results have been cross-checked and verified by numerical and particle simulations (A. Labno, M.C. Lee, and R. Pradipta, personal communication, 2006). These whistler wave-induced ionospheric effects can be diagnosed simultaneously at Arecibo and at the AGCP, using VLF/LF receivers, radars, and optical instruments (all-sky imagers). It is interesting to point out that for these particular studies, it is not necessary to deploy the VLF/LF receivers exactly at the footprint of the magnetic flux tube to detect the emerging ducted whistler waves. The aforementioned experiments on whistler wave interactions with the ionosphere and magnetosphere will be conducive to the investigation of whistler wave effects on space weather, and to advancements in nonlinear space plasma physics. Another fundamental question that needs timely resolution concerns the neutral oxygen density and temperature dilemma. Although knowledge of [O] density and temperature, Tn, in the upper thermosphere is essential for solving many fundamental problems in terrestrial-space physics, existing ground-based remote sensing techniques used to infer these neutral parameters suffer from long-standing experimental uncertainties and theoretical ambiguities. Observations using an AMISR array panel at the AGCP would remove the historical difficulties of theoretical inversion approaches in particular, and they have the potential to provide a routine and reliable means for thermospheric parameter estimation. Specifically, empirical constraints on photoelectron (PE) flux, as derived from simultaneous ISR measurements of both the local and conjugate hemispheres, allows much more accurate parameter estimation via photochemical model inversion of passive optical observations of airglow emissions that are excited by photoelectron impact.  The need for improved forward modeling of the PE flux is motivated by significant discrepancies between observed O I 844.6 nm emission brightnesses and photochemical model predictions of its brightness by both the GLOW (S. Solomon) and FLIP (P. Richards) models. The 844.6 nm airglow emission, which is excited almost exclusively by PE impact, has been observed for decades at the Arecibo Observatory, whereNcalculations of its local PE impact production are well constrained by the Arecibo ISR. However, the lack of empirical information regarding the conjugate hemisphere PE flux is a likely source of the apparent model inaccuracy. Variations in the observed 844.6 nm brightness cannot be modeled straightforwardly in terms of [O] as inverse theory demands. By using AMISR to measure the conjugate PE flux that contributes to 844.6 nm emission excitation, the feasibility of twilight [O] estimation via photoelectron model inversion of 844.6 nm brightness measurements is significantly more promising. Similarly, neutral temperature estimation from line profile analysis of the upper thermospheric metastable helium emission at 1083 nm also benefits from more accurate forward modeling of its dominant PE impact source. The non-negligible contribution of He+ recombination to metastable helium atom production renders traditional Doppler temperature analysis ambiguous, since the resulting hot recombinant metastable atoms are likely to emit a 1083 nm photon before thermalizing to the ambient neutral temperature. As a result, accurate Tn estimation relies on inverting a forward model of metastable helium production under both recombination and PE impact sources. While the Arecibo ISR yields measurements of local PE flux, He+ density and ion temperature as model constraints, the historical lack of information regarding conjugate PE production has hindered Tn estimation from 1083 nm line profile measurements to date. An AMISR array panel at the geomagnetic conjugate location of the Arecibo Observatory would provide needed constraints on PE flux, which in turn will yield an important and long overdue means for thermospheric remote sensing using combined optical and radar measurements.

   In addition to the height-layer bands described above, a second type of structure has been observed in the tropical ionosphere over Arecibo during heightened geomagnetic activity. This is usually referred to as “intense mid-latitude spread-F”. While the height-layer bands do not greatly disturb the total electron content (TEC) overhead, these intense mid-latitude spread-F events create depletions, not only in the nightglow, but also in the TEC. As seen in Figure 8,

gradients as large as 20 TECU over 10s of kilometers have been observed. Such structures almost certainly will have detrimental effects on navigation systems such as the Global Positioning Satellite system. Occurring less frequently than the height-layer bands, these structures are not as well-characterized and much still needs to be learned about them.

   Studying these phenomena in the American sector from conjugate sites outfitted with a complimentary set of optical and radio instruments, including conjugate incoherent scatter radar facilities, may be the only way to come to a complete understanding of these intriguing and important types of disturbances in the mid-latitude ionosphere.

   There are further scientific motivations for the installation of an UAF at the AGCP related to the study of the neutral atmosphere because this facility would be located inside one of the most dynamically active regions on the planet. This is shown in the global momentum flux distribution estimated by Ern et al. (2004) and reproduced in Figure 9. Because of the critical role of GW momentum fluxes in controlling the mesospheric circulation, thermal structure, and variability, and in anticipated (but unproven) influences on tidal and PW structures, its quantification at a wide range of latitudes is perhaps the most pressing need in understanding and accounting for these dynamics in large-scale models of the MLT. Specifically, of greatest need are long-term measurements quantifying momentum fluxes (zonal and meridional) on short time scales that enable 1) evaluations of their responses to filtering by tidal and PW wind fields, 2) measures of the vertical divergence of these fluxes that influence the tidal and PW amplitudes and phase structures themselves, and 3) the mean momentum fluxes in the presence of tidal and PW modulation that impact the zonal mean circulation and thermal structure as a function of latitude, tidal and PW activity, and season. This suggests that the region extending from La Plata, Argentina and over the Antarctic peninsula may be among the most active, interesting, and important regions at which to quantify GW influences of any site on the planet. Further evidence of the importance of this region is provided by the optical estimates of Espy et al. (2006).

   The study of MLT chemistry and its relation to the micrometeor mass input into the upper atmosphere is also a field which will greatly benefit from such a facility. It is now widely accepted that sporadic extraterrestrial particles in the size range of 10-11 to 10-4 g are likely to be the major contributors of metals in the MLT.

   It is also well established that this material gives rise to the upper atmospheric metallic and ion layers observed by radars and lidars. In order to understand how this flux serves as the physical stimulus for the atmospheric phenomena, accurate knowledge of the global meteoric input function (MIF) is critical. The MIF accounts for the annual and diurnal variations of meteor rates as a function of latitude, directionality, velocity and mass distributions. Estimates of most of these parameters are still under investigation. A set of predictions of the diurnal and seasonal micrometeor rate as a function of latitude are shown in Figure 10. These predictions, which are derived from a model of the global MIF recently reported by Janches et al. (2006), are presented for every 5˚ in latitude for the 15th of each month at a longitude of ~66˚ W. In this picture a seasonal variation is observed which is largest at higher southern and northern latitudes. For example, in February, the predicted meteor activity increases at southern latitudes greater than 50 degrees, reaching a maximum in March (southern hemisphere autumn) and a minimum in September (southern hemisphere spring). A very similar behavior is shown in the northern hemisphere where the maximum is reached during the autumn months (September) and the minimum around spring (March). At theses high latitudes, once the activity is intense, the diurnal variability is lower. In particular, at or near the poles the model predicts practically no diurnal variability as measured and reported by Janches et al. (2004b). At the equator the seasonal variation predicted by the model is negligible, while at mid latitudes it is similar to those measured by HPLA radars (Janches et al., 2006). Global coverage of meteor observations is needed to map the MIF precisely and improve our existing models. An AMISR at the AGCP would provide crucial observations at southern latitudes, essential for the precise modeling of the MIF and its relation to the atmospheric phenomena mentioned above.

3. Existing and Planned Argentine Support.

   Although individual collaborations between ionospheric researchers and students in the United States and Argentina have been active for a long time, this Workshop gave the opportunity for joint discussions about the interests of both communities. In so doing, it built the foundation for a major, joint, initiative. Many of the prominent ionospheric researchers from Argentina were present at the Workshop; they took advantage of the opportunity to give a comprehensive overview of the main scientific interests of the Argentine ionospheric community. It was a pleasure for all present at the Workshop to discover that the Argentine scientific interests complement very well those of the US community and share the emphasis and need towards establishing the AGCP-UAF. Although the Argentine ionospheric research community has been active for more than 50 years, it was stressed that the installation of an AMISR and other experimental facilities in Argentina would encourage a rebirth of interest in Aeronomy Research in the country. This would occur through a joint effort of national groups active in the field and the collaboration of external partners. This effort would crystallize in a “Programa Argentino de Investigaciones Aeronómicas” (PRARIA), under the sponsorship of national organizations with the participation of external partners. The research groups initially involved in PRARIA, all of which were represented at the Workshop, are: 1) CASLEO, Conicet, San Juan; 2) GESA, Universidad Nacional de La Plata; and 3) GASUR-UTN Facultad Regional Tucumán. The totality of this group has the potential to obtain institutional and financial support at the national level in Argentina sufficient to assure the sustainability of the partnership effort. In all the presentations by the Argentine colleagues, evidence of their impact on ionospheric data from Argentina was shown.

   An AMISR located in Argentina together with simultaneous ionosonde, optical instruments, lidars and GPS receivers in several other locations would provide the substantial scientific information needed to address important questions related not only to geomagnetic physics but also to the effects of the anomalies (Appleton and South Atlantic).

   As discussed in the next section there are two possible ideal strategic locations for these research endeavors. To sustain increased ionospheric scientific research in Argentina, the academic training in the field would be intensified with specialized undergraduate and graduate studies at the universities in Tucumán (UNT and UTN), San Juan (UNSJ) and La Plata (UNLP). These efforts will by augmented by post graduate studies elsewhere in Argentina, in the US and in Italy. It was emphasized that the work to be carried out in Argentina under the Programa will contribute substantially to the study of the effects of the low latitude ionosphere in South America for satellite navigation and positioning applications. It was mentioned that scientific groups of the Programa are involved in feasibility studies for regional SBAS such as possible augmentation systems for single frequency operation of GNSS. Other potential applications of the studies to be carried out are related to the monitoring of Space Weather conditions through now-casting of ionospheric conditions in the region.

3.1 Potential Locations for UAF-AGCP

   We propose two locations as the principal candidates for the development of an UAF in Argentina. The main justification for these locations is based on the excellent radar beam sky coverage of the AGCP if AMISR were to be installed there, as can be seen in Figure 11. The first location, Bahia Blanca, was proposed during the workshop by the Argentine partners while the second location, La Plata, resulted from a later study of the AMISR coverage of the predicted path of the AGCP. Both locations are near large cities which provide good infrastructure for an international observatory. La Plata in particular has several strategic advantages over any other location. These are:

   • As illustrated in Figure 11, the radar coverage of the AGCP from La Plata is slightly better than from Bahia Blanca. More importantly, La Plata is located near the predicted shifting path of the AGCP (Figure 12) which suggest that the coverage at the time this effort is realized will be optimal.

   • La Plata is the capital city of the province of Buenos Aires and is located ~30 miles away from the city of Buenos Aires, capital of Argentina and from Ezeiza Airport, the major international airport in Argentina which services several cities in the US and Europe. This provides very easy access for observers.

   • The National University of La Plata is also located in this city. The university has a department of Astronomy and Geoscience (FACG) which houses one of the major ionospheric research groups in the country. Currently, the Department is developing a graduate program in Aeronomy and Space Weather. This would provide a major human resources support to the AGCP-UAF effort.

4. Steps Toward a AGCP-UAF

    • April 2006: International Community Workshop

    • Sept 2006 – June 2007: Topical mee