Browsing by Author "Cuevas, R."
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Item Open Access Combined radar observations of equatorial electrojet irregularities at Jicamarca(European Geosciences Union (EGU), 2007-03-08) Hysell, D. L; Drexler, J.; Shume, E. B; Chau Chong Shing, Jorge Luis; Scipión, Danny; Vlasov, M.; Cuevas, R.; Heinselman, C.Daytime equatorial electrojet plasma irregularities were investigated using five distinct radar diagnostics at Jicamarca including range-time-intensity (RTI) mapping, Faraday rotation, radar imaging, oblique scattering, and multiple-frequency scattering using the new AMISR prototype UHF radar. Data suggest the existence of plasma density striations separated by 3–5 km and propagating slowly downward. The striations may be caused by neutral atmospheric turbulence, and a possible scenario for their formation is discussed. The Doppler shifts of type 1 echoes observed at VHF and UHF frequencies are compared and interpreted in light of a model of Farley Buneman waves based on kinetic ions and fluid electrons with thermal effects included. Finally, the up-down and east-west asymmetries evident in the radar observations are described and quantified.Item Restricted Unexpected rapid decrease in phase velocity of submeter Farley-Buneman waves with altitude(American Geophysical Union, 2008-02-09) Kagan, L. M.; Kissack, R. S.; Kelley, M. C.; Cuevas, R.An unexpected and drastic drop in the phase velocity Vph of Farley‐Buneman (FB) waves with increasing altitude was observed in the equatorial electrojet over Jicamarca. The effect was detected with the newly employed 430‐MHz radar looking vertically. The decrease in Vph was 67 m/s and 36 m/s over 2.4 km for the FB waves moving towards and away from the radar, respectively. By contrast, the 430‐MHz data from 20° west displayed little dependence on altitude. Simultaneous observations with a 50‐MHz radar at 23° and 51° west also displayed little change of Vph with altitude. We show that electron inelastic cooling which defines gradual transition from super‐adiabatic to isothermal processes at 50 MHz (used in majority of observations), becomes unimportant at higher frequencies. The effect is evinced at radar frequencies ≥150 MHz and requires altitude resolution <2 km to be observed. Averaging over >7 km at oblique incidence masks the effect.