Browsing by Author "Ierkic, H.M."

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    Fixed heigth S-band radar observations of the stratosphere
    (Instituto Geofísico del Perú, 1990) Ierkic, H.M.; Gierasch, P.J.; Woodman Pollitt, Ronald Francisco
    It is now known that turbulence and mixing in the lower stratosphere occurs in intermittent layers of thickness between about 30 and 300 meters. Layered structures also exist in the ocean (Woods, 1969) and in the atmospheres of the other planets (Gierasch and Conrath, 1987). It appears that dissipative processes in stratified geophysical fluids frequently take place in thin layers. It is therefore of great importance to observe and document the nature of these dynamical regions. The Arecibo facility is uniquely capable of performing these high resolution measurements. The S-band radar system has been configured for high resolution studies of the lower stratosphere, and data have been collected and analyzed, demonstrating its potential and capabilities. Previous e:ffort was directed to a description of a wide region of the at­mosphere, with only brief attention dedicated to continuous observations of a particular height. We propose a new series of observations focusing on the time evolution of waves and turbulence at a fixed altitude. The mode of operation that best meets this objective is "Fixed mode pointing," as described by lerkic et al. (1990) (attached as an Appendix), and no new techniques need to be developed.
    Palabras clave:RadarStratosphereTurbulence
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    Observations of the HF-enhanced plasma line with a 46.8MHz radar and reinterpretation of previous observations with the 430 MHZ radar
    (American Geophysical Union, 1982) Fejer, J.A.; Ierkic, H.M.; Woodman Pollitt, Ronald Francisco; Röttger, J.; Sulzer, M.; Behnke, R.A.; Veldhuis, A.
    During 5.1 MHz HF transmissions below the F-region penetration frequency by a nearby ionospheric modification facility, radar echoes coming from F-region heights at a frequency of 46.8 + 5.1 = 51.9 MHz were received while a VHF radar using the 305 m spherical reflector at Arecibo was transmitting pulses coherently on 46.8 MHz. The bandwidth of the echoes was less than 10 Hz. The so-called decay line due to the parametric decay instability was expected at a frequency lower by about 300 Hz but it was not observed. Density variations caused by the ponderomotive force resulting from the standing wave pattern at 5. 1 MHz were tentatively invoked to explain the observations. Poorly understood aspects of previous analogous observations with the 430 MHz radar can be similarly explained.
    Palabras clave:RadarIonosphereEchoes