The self-focusing instability in the presence of density irregularities in the ionosphere
Abstract. The self-focusing instability of high-power radio waves in the ionosphere in the presence of density irregularities is presented. The present study addresses the role of preexisting density irregularities which are always present in the instability region. The presence of ambient irregular...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1082.2431 http://spp.astro.umd.edu/SpaceWebProj/CV_PapaDoup_links/50_The%20Self-Focusing%20Instability%20in%20the%20Presence%20of%20Density%20Irregularities%20in%20the%20Ionosphere.pdf |
| Summary: | Abstract. The self-focusing instability of high-power radio waves in the ionosphere in the presence of density irregularities is presented. The present study addresses the role of preexisting density irregularities which are always present in the instability region. The presence of ambient irregularities results in the excitation of wave numbers, which, on the basis of homogeneous theory of the self-focusing instability, should be stable. This effect can explain the puzzling observations that indicate growth of the medium-scale (on the order of hundreds of meters) irregularities during ionospheric heating. The computational results are compared with available experimental data and will be used to plan experiments using the upcoming High-Frequency Active Auroral Research Program heater. Introduction The ionospheric modification experiments using radio frequency (RF) heater facilities at Arecibo, Platteville, Alaska, the SURA facility in Russia, and Tromso provide a rich variety of results related to the spatial structures in the ionospheric medium, the scattered electromagnetic signals, and particle energization [Lityak, 1970 Current theories emphasize identification of the physical processes leading to self-focusing in homogeneous plasmas. They have often not considered many realistic effects, such as density irregularities in the medium. These nonideal factors affect the self-focusing instability, because they affect the local refractive index of the plasma. In the present paper we study the self-focusing of radio waves in the ionosphere for the underdense (pump frequency, Wo, much greater than the plasma frequency, Wpe) case in two dimensions (2D). The 2D geometry captures the essential physics aspects of the selffocusing instability. We find that the presence of density irreg- They included an initial sinusoidal perturbation of the density in the case of underdense plasma when the pump wave was represented by a plane wave. This density perturbation leads to the linear growth of the self-focusing instability ... |
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