Statistical investigations of layer-type and clump-type plasma structures of 3-m field-aligned irregularities in nighttime sporadic E region made with Chung-Li VHF radar
| Autor: | Yen Hsyang Chu, Ruey Ming Kuong, Ching Lun Su, Chien-Ya Wang, Kuo Feng Yang, H.-C. Chen |
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| Rok vydání: | 2011 |
| Předmět: |
Atmospheric Science
Soil Science Aquatic Science Oceanography Spectral line law.invention symbols.namesake Geochemistry and Petrology law Earth and Planetary Sciences (miscellaneous) Radar Field aligned irregularities Earth-Surface Processes Water Science and Technology Line (formation) Physics Ecology Paleontology Forestry Plasma Sporadic E propagation Geodesy Horizontal plane Computational physics Geophysics Space and Planetary Science symbols Doppler effect |
| Zdroj: | Journal of Geophysical Research: Space Physics. 116 |
| ISSN: | 0148-0227 |
| DOI: | 10.1029/2011ja016696 |
| Popis: | [1] With interferometry measurements made with Chung-Li 52 MHz VHF radar, characteristics of layer-type and clump-type plasma structures of 3-m field-aligned irregularities are investigated for the first time. Long-term statistics show that the thickness and the zonal extent of the layer-type plasma structures are in the ranges of approximately 0.1–4 km and 5–28 km, respectively. However, the vertical and zonal extents of the clump-type plasma structure are comparable with each other, ranging from 2 to 12 km. These features clearly imply that the cross sections of the layer-type and clump-type plasma structures intercepted by a fan-like effective radar beam are, respectively, in highly elongated and nearly circular shapes. The mean height of the clump-type plasma structures is slightly higher than that of the layer-type plasma structures by about 5 km. From interferometry-measured echo distributions about the perpendicularity to the local magnetic field line, it is found that the mean aspect angle of the 3-m field-aligned irregularities for the layer-type plasma structures is about 0.05° smaller than that for the clump-type plasma structures. In addition, the height dependence of the aspect angle of the layer-type plasma structures is different from that of the clump-type plasma structures. The former tends to increase with height, while the later decreases with altitude. The zonal trace velocities of the layer-type and clump-type plasma structures estimated from their temporal displacements in the horizontal plane are, respectively, in ranges of −150–100 m/s and −180–80 m/s, in which negative (positive) values indicate eastward (westward) drift. The characteristics of the Doppler spectra of the echoes from the layer-type and clump-type plasma structures are also analyzed and the relations between the spectral parameters and the aspect angles are also discussed in this article. |
| Databáze: | OpenAIRE |
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