Virtual ISR

Ionospheric empirical models are important tools for many research, engineering and educational efforts. Local and regional models can better represent unique features that may be easily smeared out in global models, and are important complements to and validation tools for global models. As one of the most powerful ground-based instruments for probing the Earth's upper atmosphere, incoherent scatter radar directly measures ionospheric electron density Ne, electron and ion temperatures Te and Ti, and line-of-sight ion velocity over a broad range of altitudes. Long-term ISR observations provide an extremely valuable data source for addressing significant scientific issues related to ionospheric and thermospheric climatology. Since the development of incoherent scatter radars in the 1960's, long-term observational data sets have been accumulating. Based on these data, much progress has been made in recent years in constructing empirical ionospheric models. So far, local empirical models for 7 ISR sites have been developed.

Regional ionospheric models over Millstone Hill area have also developed based on the radar's fully steerable antenna which provides a geographical latitudinal coverage of 35-55. Using appropriate mathematical approximations, local models from similar longitudes in America can be combined to form an American Regional Model (ARM). This has been accomplished by combining (1) Arecibo local model, (2) Millstone Hill local model, (3) Sondrestrom local model, (4) Millstone Hill regional model, and (5) an additional 4 models based on observations to the north and to the south of Sondrestrom, and of Arecibo.

Large scale magnetospheric electric fields result from interactions between the solar wind and embedded interplanetary magnetic field (IMF) and the Earth's geomagnetic field. Studying and modeling the high latitude convection pattern are critically important for various space weather efforts. New high latitude convection models and patterns have been obtained based on a composite analysis of ISR observations in the North America sector at Millstone Hill and Sondrestrom. These observations span a combined latitude range between 55o-78o over time periods starting from 1978 for Millstone Hill and from 1995 for Sondrestrom. This model, regional to the American Sector, represent average and steady patterns of the convection as driven by the IMF By and Bz or by the Kp and the By direction.

All ISR models are online for free access at http://madrigal.haystack.mit.edu/models/. Virtual ISRs provide model estimates of the ionospheric conditions for the current time over each site (local and regional ionospheric variations) or high latitudes (plasma convection). They are computed based on near-real-time F107 and ap, or IMF By and Bz from the ACE satellite, and are updated every 15 min (or 1 hour for the convection). Animations of ionospheric profiles display changes in the past 24 hours and are updated accordingly. Model runs can be also performed from a web interface where users can key in inputs.

Real-time true ISR data and VISR (model) data comparisons are also provided when an ISR experiment is being performed at Millstone Hill. See the model website, or http://madrigal.haystack.mit.edu/models/RealDataVsModel/. The model-based VISR result provides an excellent reference for radar operators to virtually monitor the ionospheric conditions under which the radar is working, and can be used as a handy tool to assess the radar's performance and data quality.

References

Zhang, S.-R., J. M. Holt, A. P. van Eyken, M. McCready, C. Amory-Mazaudier, S. Fukao, and M. Sulzer, Ionospheric local model and climatology from long-term databases of multiple incoherent scatter radars, Geophys. Res. Lett., 32, L20102, doi:10.1029/2005GL023603.PDF

Zhang, S.-R., J. M. Holt, A. M. Zalucha, and C. Amory-Mazaudier, Mid-latitude ionospheric plasma temperature climatology and empirical model based on Saint Santin incoherent scatter radar data from 1966-1987, J. Geophys. Res., 109, A11311, doi:10.1029/2004JA010709, 2004. (Full Paper: PDF)

Zhang, S.-R. and J. M. Holt, Ionospheric temperature variations during 1976-2001 over Millstone Hill, Adv. Space Res., 33, 963-969, 2004. DOI 10.1016/j.asr.2003.07.012 (Full Paper: PDF file )

Holt, J. M., S.-R. Zhang, and M. J. Buonsanto, Regional and local ionospheric models based on Millstone Hill incoherent scatter radar data, Geophys. Res. Lett., 29(8), 10.1029/2002GL014678, 2002.

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