Plasma structures of 3-meter type 1 and type 2 irregularities in nighttime midlatitude sporadic E region

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Title:	Plasma structures of 3-meter type 1 and type 2 irregularities in nighttime midlatitude sporadic E region
Authors:	Chu Y.H. Wang C.Y.
Contributors:	物理系
Keywords:	ionospheric irregularities plasma waves and instabilities interferometry radar atmosphere physics
Date:	2002
Issue Date:	2009-12-04 15:37:37 (UTC+8)
Abstract:	Although the plausible mechanisms involved in the generation of midlatitude type 1 sporadic E (Es) irregularities have been suggested, rare observational evidence is provided to validate the proposed plasma structure associated with the midlatitude type 1 Es irregularities. In this article, the type 1 echoes observed by the Chung-Li VHF radar located in the equatorial anomalous region are interferometrically analyzed and the corresponding plasma structure of the type 1 irregularities is reconstructed. We find that the plasma structure has sharp lateral and top and bottom boundaries with thickness of about 1-2 km and horizontal extent of about 3-5 km in E-W direction. Its dimension in N-S direction cannot be resolved by using interferometry technique because of considerably narrow width of expected echoing region in elevation. The observed Doppler velocity of the type 1 echoes can be as low as 220 m/s, substantially smaller than nominal ion acoustic wave speed (about 360 m/s) in Es region. The spatial structure of the concurrent type 2 irregularities is also reconstructed. The result strongly suggests that it be a well-defined thin layer with thickness of 1-2 km and horizontal extent of 9-17 km in E-W direction, very different from that of the type 1 irregularities. The whole structure of type 1 irregularities moves bodily toward east at speed of about 31 m/s, and no vertical displacement of the structure is observed. Although the movement of the layer structure of the type 2 irregularities in E-W direction is indistinct, it descends remarkably at a rate of 10.3 m/s. These features imply that for the present case the factors governing the dynamic behavior of the type 1 and type 2 irregularities are different and independent, irrespective of the fact that the clump of the type 1 irregularities separates from that of concurrent type 2 irregularities only by about 4 km in distance.
Relation:	JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Volume: 107 Issue: A12 Article Number: 1447
Appears in Collections:	[Department of Physics ] journal articles

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