Open AccessPlasma structures of 3‐meter type 1 and type 2 irregularities in nighttime midlatitude sporadic E region
Author(s) -
Chu YenHsyang,
Wang ChienYa
Publication year - 2002
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002ja009318
Subject(s) - sporadic e propagation , middle latitudes , geology , geodesy , type (biology) , plasma , displacement (psychology) , radar , latitude , vertical displacement , physics , geophysics , doppler effect , optics , geometry , ionosphere , atmospheric sciences , astronomy , mathematics , psychology , paleontology , telecommunications , quantum mechanics , computer science , psychotherapist
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.