Proceedings with Extended Abstracts (single PDF file) - Radio ...

STUDY OF A LOW E-REGION QUASI-PERIODIC EVENTFROM CAMP SANTIAGO, PUERTO RICOJulio Urbina 1 , Erhan Kudeki 2 , and Steven J. Franke 21 Donaghey College of Information Science and Systems Engineering, University of Arkansas, USA2 Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois, USA1 IntroductionRecent papers by Patra et al.[2002], Pan andRao[2002], Rao et al.[2000], and Urbina et al.[2000]).describe quasi-periodic VHF radar backscatter fromlower E-region plasma irregularities detected at anumber of low and mid-latitude radar sites. Thisnewly discovered class of VHF radar echoes is observedbelow 100 km altitude and is referred toas “LQP” to distinguish it from better known QP(quasi-periodic) radar signatures detected at upperE-region heights [e.g., Yamamoto et al.[2001]]. Atpresent there is considerable uncertainty about thegeneration mechanisms of LQP as well as the interpretationof LQP data sets. Uncertainties indata interpretation mostly originate from potentialrange/height ambiguities and/or the lack of knowledgeabout the background ionosphere where LQPirregularities grow.The purpose of this paper is to offer an in depth discussionof a multi-sensor data set collected duringan LQP event in an attempt to address some of thedifficulties just mentioned. The event, first reportedin Urbina et al.[2000], was observed with a 50 MHzradar interferometer (RI) operated from Camp Santiago,Puerto Rico, while simultaneous electron densitymeasurements were being conducted nearby in the E-region with the 430 MHz Arecibo incoherent scatterradar (ISR). Figures 1 and 2, discussed in detail inSection 2, show some aspects of the experiment geometryas well as ISR and RI observations. The discussionin Section 2 is focused on the information extractedfrom different sensors and Section 3 exploresthe relationship between different sensor outputs. AnLQP backscattering scenario compatible with all theobservations is constructed and discussed in Section4. It is shown that the observed event could not havebeen initiated by a gradient-drift plasma instability20.5019.50-68 -67 -66 -6518.50TA17.50Figure 1: A map showing the Coqui 2 experiment geometryat E-region heights: Solid line segments indicatethe geographical coordinates (longitude and latitude)where the viewing directions from the CampSantiago (S) system cross the Earth’s magnetic fieldat an angle of 90 o at radar ranges 120, 130, 140, ...,200 km and between the first nulls of the gain patternsof the transmitting antenna. The dashed contoursdepict the geographical coordinates of perpendicularityat 90, 95, 100, ..., 140 km altitudes.process despite the presence of sharp gradients in thebackground electron distribution.2 Multi-sensor observations ofan LQP eventThe location of the 50 MHz Camp Santiago radar interferometer(RI) is marked with an “S” in Figure 1.As discussed in detail in [?] the interferometer consistedof two antenna arrays with a 50 m east-westSR90