MRI: Development of a High Resolution Radio Imaging System for the Study of Ionospheric Radio Emissions and Structure

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Ionized plasmas make up 99% of the directly observable matter in the universe, and a better understanding of turbulence in nearby space plasmas can be applied to many space and astrophysical environments, and to technological problems such as magnetic spacecraft radiation shielding, propulsion (ion engine, solar sail), improving space-to-ground communication and navigation (GPS) links, device fabrication, and fusion energy generation. A new high-power, high-frequency transmitter at the Arecibo Observatory in Puerto Rico offers opportunities to study ionospheric plasmas in a carefully controlled way. This award is for the development of a six-element medium and high-frequency (MF/HF, 0.3 to 30 MHz) imaging radio array. There will be three primary uses of the array: (1) Imaging and spectral and temporal study of radio emissions generated within the relatively narrow beam (about 10-deg full width) of the new Arecibo Observatory transmitter during ionospheric radio wave interaction experiments (heating campaigns); (2) Oblique-angle radio emission observations and multiple bistatic radar observations with an HF radar in Cayey, Puerto Rico; and (3) Direction-finding radio emission observations and radar imaging studies of the ionosphere within the wide transmitter beam of the HF radar in Cayey. Arecibo Observatory HF campaigns are anticipated to be twice a year for about two weeks each, so imaging with multi-kilometer-scale spacings would be done then, using temporary field sites. 20-km to 100-km spacings would also be done using temporary field sites, at least initially. At other times the array would be located at a permanent site at the Interamerican University campus in Aguadilla, Puerto Rico, where 10-m to 300-m antenna spacings would be used. The 12-km array (array 1) would image the structure of stimulated radio emissions (SEE) from the HF interaction region with the goal of determining the exact geometries of the source regions of the many SEE spectral features with respect to the geomagnetic field. The array would also show whether or not the polarization of SEE varies between spectral features. Radio images of the geometric and polarization properties of the emissions promise to reveal new details of the physics of the emissions. The Bayamon and Aguadilla campuses of Interamerican University of Puerto Rico are private, primarily undergraduate institutions with nearly all Hispanic, mostly low-income students. The instruments to be developed would enhance the overall capabilities of the atmospheric, space, and radio research infrastructure at Interamerican, including the ongoing development of a graduate program emphasizing atmospheric and space research.