Theoretical and Experimental Study of Gravity Waves in the Ionosphere Observed With Incoherent Scatter Radar
In the Worldwide Atmospheric Gravity Wave Study (WAGS) campaign, the source-response relationship between the auroral activities and the gravity waves observed in the ionosphere was studied. Ionospheric parameters observed with the incoherent scatter radars at Sondrestrom and Millstone Hill were compared with predicted results based on gravity wave theory. In the observed data, usually two types of disturbances can be identified. One is the distinct, semiperiodic traveling ionospheric disturbance. The other is the ever-present, semirandom perturbations. The first type will be classified as the "special event," and one which was observed on October 18, 1985 during a moderately magnetic active period will be analyzed. The second type will be classified as the "background wave spectra," and these spectra under various levels of magnetic activity will be analyzed. The observed parameters used in this study are the ionization density and the line-of-sight ion velocity. This provides more information than in most of the previous investigations of traveling ionospheric disturbances, in which only electron density perturbations were used. The data will be analyzed and compared with theoretical models to yield information about the special gravity wave event such as the vertical and horizontal wavelengths, the horizontal phase and group speeds, and the kinetic energy density carried by the waves. The observed waves at the two radar sites are related to a possible source region in the auroral zone. It will be shown that the neutral vertical velocity spectrum can be modeled as a power-law type of spectrum. The overall kinetic energy of this spectrum will be calculated and compared with that associated with the special event observed on a magnetically active day.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign