Collaborative Research: Intermediate Scale Structures in the Auroral Oval and the Ionospheric Trough

点击翻译按钮获取中文摘要

The project aims to investigate the occurrence and distribution of intermediate scale irregularities that develop on the equatorward edge of the aurora and in the midlatitude trough. A network of six passive radio beacon receivers in the northeast United States will be used to assemble a database which will then be interrogated to establish the morphology of the intermediate scale structures. A particular goal is to determine the relation of the zonal variations of the structures to the source region, such as the auroral oval or the trough, and to the level of geomagnetic activity. The database comprises measurements of the total electron content (TEC), phase scintillations, and the rate of TEC fluctuations which will be obtained by monitoring radio beacon transmissions at 150 MHz and 400 MHz from low-Earth-orbiting satellites. Five of the receivers to be used in the investigation already exist; the project seeks to establish a sixth receiver in upstate New York. The receivers are Coherent Ionospheric Doppler Receivers, or CIDRs, and the network of six CIDRs established under this project will constitute the North East CIDR Array (NECA). The locations of four of the receivers are Cornell, SUNY-Oneonta, Siena College, and MIT. These are distributed over about 400 km of longitude at a geomagnetic latitude of ~54 degrees north. This array configuration enables measurements of the occurrence and spatial distribution characteristics of intermediate scale plasma irregularities, ranging in size from 100 m to 30 km. A southern CIDR has been deployed at Wallops Island, at roughly 4 degrees southern magnetic latitude, and a sixth CIDR will be established in the Adirondacks of Northern New York (2 degrees north magnetic latitude) in the fall of 2007. Data from the receivers will be used to determine the approximate altitude of observed scintillations and fluctuations. Once the approximate altitude has been determined, the observed scintillation can be located in geomagnetic latitude and longitude, as well as in position relative to the auroral oval, the ionospheric trough, and the storm enhanced density (SED) plumes. The broader impacts of the project are both educational and societal. The investigation will contribute to the determination of causes of space weather processes that specifically impact technologies on Earth and in near-Earth space. Ionospheric irregularities produce scintillation in radio communication and navigation systems and generate "clutter" in radar signals. Such systems are ubiquitous in the air travel industry. Since there are increasing levels of air travel near the auroral oval and ionospheric trough, the morphology and occurrence of plasma irregularities in these regions has societal implications as well as scientific merit. A central database will be established to store all the NECA observations which will be freely and publicly available. The project will involve undergraduates in all aspects of the investigation, including data acquisition, archiving, processing, and quality control. This will enable participating students to become familiar with the instrumentation and data as well as develop their scientific and technological competence.