Browsing by Author "Hysel, D. L."
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Item Restricted Improved electron density measurements at Jicamarca(American Geophysical Union, 2007-11-27) Rodrigues, F. S.; Nicolls, M. J.; Hysel, D. L.Taking into account the effects of electron Coulomb collisions, incoherent scatter (IS) radar cross sections for probing angles close to perpendicular to the magnetic field have been calculated and used to correct backscattered power profiles measured with the Jicamarca incoherent scatter radar so that they accurately represent the height variation of the ionospheric electron density. The corrected power profiles are compared with simultaneous Faraday rotation measurements of electron density. The profiles agree within the measurements uncertainties. This result improves electron density measurements at Jicamarca, since power measurements are less sensitive to clutter and interference than Faraday rotation measurements. The results can be used to correct Jicamarca long‐term IS power measurements.Item Restricted Seeding and layering of equatorial spread F by gravity waves(American Geophysical Union, 1990-10) Hysel, D. L.; Kelley, M. C.; Swartz, W. E.; Woodman Pollitt, Ronald FranciscoStudies dating back more than 15 years have presented evidence that atmospheric gravity waves play a role in initiating nighttime equatorial F region instabilities. This paper analyzes a spectacular spread F event that for the first time demonstrates a layering which, we argue, is controlled by a gravity wave effect. The 50-km vertical wavelength of a gravity wave which we have found is related theoretically to a plasma layering irregularity that originated at low altitudes and then was convected, intact, to higher altitudes. Gravity waves also seem to have determined bottomside intermediate scale undulations, although this fact is not as clear in the data. The neutral wind dynamo effect yields wave number conditions on the gravity wave's ability to modulate the Rayleigh-Taylor instability process. Finally, after evaluating the gravity wave dispersion relation and spatial resonance conditions, we estimate the properties of the seeding wave.