This project will undertake an upgrade to and continued science investigations with the VHF Cornell University Portable Radar Imager (CUPRI) which will be relocated to Cornell University in Ithaca, NY from Puerto Rico. The primary science focus is high latitude E region plasma instabilities which will be studied through observations of the radar echoes observed by CUPRI. The origin of the echoes remains a subject of debate; until recently, the irregularities were believed to be created during intense energetic particle precipitation. However, two new mechanisms have been proposed. The first involves the generation of instabilities by the steep plasma density gradients associated with storm-enhanced density (SED) structures. The SED features have been observed from the tropics to well beyond the plasmapause. Given the right electric field conditions, the SEDs may cause the plasma to go unstable, creating the small-scale structures required to enhance radar backscatter. Alternatively, there may be a second mechanism responsible for driving plasma instabilities: a temperature gradient instability that has been observed to produce HF scattering over the SuperDARN radar at Wallops Island. These space weather events can result in degraded communication and navigation systems as the primary instabilities cascade to smaller scale lengths, producing scatter with consequential multi-path interference. In addition to investigating the origin of the perturbed echoes, the project will explore three other science questions: (1) do auroral events created by intense energetic particle precipitation, like those previously observed by CUPRI along the poleward edge of visible auroral arcs, relate to, or are they distinguished from, SED structures? (2) will images obtained by CUPRI be correlated with perturbations in total electron content during significant space weather events? (3) can more be learned about auroral plasma physics from measurements of magnetic aspect angles, as has been observed at Jicamarca Radar Observatory? (4) does the temperature gradient instability that causes some of the HF scattering observed over the SuperDARN radar at Wallops Island play a role in VHF scattering observed from Ithaca? The planned upgrades to the CUPRI system include (1) deploying additional antennae and receivers to enable 3-D imaging of the echoes as well as measurements of the magnetic field aspect angle sensitivity of the echoes; (2) replacing analog receivers with digital receivers for improved quality control of the data from different antennae; (3) networking the data acquisition system to provide wide access, including student access, to real time and processed data products; and (4) creating a large networked database. The broader impacts of the project include the provision of extensive hands-on experience in developing, deploying, operating, and maintaining modern radar equipment to graduate and undergraduate students, as well as opportunities in data acquisition, analysis and interpretation. The host institution has demonstrated a strong commitment to including underrepresented groups in its research activity, particularly women and Hispanics, which is expected to continue under this project.
NSF Grant 073769 helped fund the Cornell University Portable Radar Interferometer, or CUPRI for short, for its development, deployments, data acquisition, analysis and interpretation for studies of the characteristics of plasma waves in the ionosphere occurring from 100 km (E-region) to over 1000 km (equatorial spread-F) in altitude from various locations around the world, including Canada, Greenland, Norway, Sweden, Brazil, Kwajalein (Western Pacific, Marshall Islands), Puerto Rico, and St. Croix, as well as near the Cornell University campus in Ithaca, NY, and in other U.S. locations. These plasma waves are aligned along the Earth’s magnetic field and require that the radar beam to be directed close to perpendicular to the magnetic field. The waves are generated by plasma instabilities (e.g., gradient-drift and two-stream Farley-Buneman) depending on locations that have included polar, mid-latitude, and equatorial latitudes. CUPRI measurements of the plasma-wave characteristics provided important clues for developing theories and models of the waves. Intense plasma-wave activity affects radio communication paths transversing the ionosphere and can create such strong interference that communication paths and navigation signals (e.g., GPS) can be disrupted. Hence the importance of understanding the theory and occurrence probabilities behind the intense plasma wave activity. These measurements were just one step in the development of predictive models that will help explain the occurrence and develop solutions for minimizing the interference in signals, such as improved algorithms for switching over to secondary systems. One very important finding was that the Doppler shift of type-I plasma waves decreased with increasing height. Previously, it was thought that these Doppler shifts followed the height dependence of the acoustic speed which is related to the increasing temperature with height. This CUPRI result was followed by others making measurements in other locations that have confirmed this result and extensive theoretical work. The CUPRI research project was run by the School of Electrical and Computer Engineering at Cornell University, which added to the considerable instrumentation and ionospheric data collection and interpretation experience that the staff and students have gained over many years working in this highly technologically-driven field. One added-value realised by the students working on the CUPRI project was the access to advanced data acquisition systems. Undergraduate and graduate students at Cornell University and collaborating institutes had gained real-time hands-on experience in the deployment and operation of advanced radar tools. Once data was collected many students were involved in the analysis and interpretation of the data as they studied upper atmospheric space weather events. Another added value was the radar experience the CUPRI gafe that contributed to the textboot "Electromagnetic Fields and Waves" by W. E. Swartz, M. C. Kelley, and F. Rana, the to "Companion Slides for Teaching Electromagnetic Fields and Waves" by W. E. Swartz and F. Rana, both published by McGraw-Hill in 2012 (ISPNs 13: 978-0-07-340898-9 and 13: 978-0-07-340899-6). Problems that could be addressed in the future by a radar interferometer like CUPRI were addressed in "A Convenient and Transportable Research Tool" (Swartz, W. E., International Innovation, 99-101, 2012). Other publications from this research are listed elsewhere.
