The investigators will study physical processes in the 120-180 km region of the atmosphere, particularly the intermediate layer, an ionization layer present at mid-latitude in this altitude range. Although the incoherent scatter radar (ISR) observations at Arecibo show that the intermediate layer forms practically every day, its composition, structure, and formation mechanism are still not well understood. The investigators will use the Arecibo ISR, in conjunction with lidars and all-sky imagers, to determine the ion composition of the intermediate layers, to develop a one-dimensional metallic ion circulation model, and to study the horizontal inhomogeneity of intermediate and their relation to gravity waves in the E and F valley region. The project will lead to improved knowledge about vertical metallic ion distribution, the intermediate layer composition, and formation mechanism. It would also improve general understanding of atmospheric dynamics related to gravity wave, tides and planetary wave, since the long lifetime of metallic ions makes them a good tracer to study the dynamics at various scales. Many aspects of the research will be directly integrated into several courses at the Electrical and Computer Engineering (ECE) Department at Miami University. Radar coding techniques to increase the signal-to-noise ratio will be incorporated into an online junior level course, Signals and Systems. A new method that is superior to wavelet analysis in analyzing non-stationary signals will be part of the Digital Signal Processing course for senior/graduate students. Many aspects of the research will be included in a new senior/graduate level course, Atmospheric Remote Sensing, to introduce students to the field of aeronomy and as undergraduate senior capstone projects topics. Also, the online course will be made available free to Central State University, a historically black university, through the Ohio 3rd Frontier Network. All the ISR data will be made publicly available.
This project uses the world’s most powerful radar, located in Arecibo, Puerto Rico, and lidars to study the physics and the chemistry of the atmospheric region between 80 km to 600 km. The radar detects echoes from electrons and ions in the ionosphere to measure the plasma velocity, temperature and electron concentration. The lidars detect the resonance from several metal atoms including sodium, potassium and iron in the altitude range of 80 to 115 km. The project results in 9 published journal papers, 3 submitted journal papers and nearly 30 conference representations in national and international conferences. One high-school, 4 undergraduate and 4 graduate students were involved in the project. One underrepresented student worked on the project both as an undergraduate and graduate student. In working on the project, we collaborated with over 10 scientists from three countries. In this project, we studied the effects of atmospheric tidal winds on the formation of ion layers and the peak concentration as well as the corresponding altitude of the ionosphere using incoherent scatter radar data. The ion layers, which typically have a thickness of about 1km, in the lower E-region below about 110 km are found to be mainly associated with tidal wind having a period of 24 hours while those above 110 km are found to be mainly due to the tidal wind having a period of 12 hours. The peak altitude and peak concentration of the ionosphere are strongly affected by the tidal winds, electric field and ambipolar diffusion. When the tidal wind components having different periods are aligned in a certain way, they can cause over 100 km drop in the ionosphere peak altitude after midnight. The tidal winds in the thermosphere at 250 km are strongly affected by the events happening below. When the temperature in the stratosphere rose suddenly, our results show that the diurnal tide (24 hr period) was suppressed while the semidiurnal (12 hr period) and terdiurnal tide (8 hr period) were very much enhanced. We compared the mesospheric Na and Fe layers, which exist at an altitude range of 80-115 km, by using common-volume lidar measurements made at the Arecibo Observatory. The temporal variations of the two species are highly correlated at practically all the heights although not always positively. Positive correlations occur in the bottom and top sides while negative correlation is observed in a relatively narrow region in the middle. The temporal correction of Na and Fe is found to be related to the vertical gradients of the two species. Vertical transport due to gravity waves or tides can satisfactorily explain the temporal correlation between the Fe and Na for all the altitudes. Using a temperature sensitive chemistry model, we also showed that the formation and evolution of the sporadic metallic layers are at least partially governed by the temperature structure and gravity wave activity. We also studied the effect of the ionosphere on the 2nd order GPS positioning error. Our results show that the second order errors also follow a diurnal pattern as the first order error. The minimum errors occur at around 6AM local time and the maximum errors occur between 12 noon and 3PM. Unlike the first order errors which are positive delay errors for signals arriving at all possible angles, the second error is positive for the signal arriving from the zenith and from the south, but it is negative for the signal arriving from the north. We have further studied the electric field around 120 km. The general assumption is that the electric field at this height is the same as that at higher altitude, say at 250 km. Our result, however, indicates that this prevailing assumption may not be valid.
