Relationship between propagation direction of gravity waves in OH and OI airglow images and VHF radar echo occurrence during the SEEK-2 campaign

F Onoma,S Fukao,S Saito,Y Otsuka,K Shiokawa,T Ogawa,M Yamamoto

doi:10.5194/angeo-23-2385-2005

Abstract

Abstract. We report simultaneous observations of atmospheric gravity waves (AGW) in OI (557.7nm) and OH airglow images and VHF radar backscatter from field-aligned irregularities (FAI) in the E-region during the SEEK-2 (Sporadic-E Experiment over Kyushu 2) campaign period from 29 July to 9 August 2002. An all-sky imager was operated at Nishino-Omote (30.5 N, 130.1 E), Japan. On 14 nights, 17 AGW events were detected in OI and OH airglow images. AGW propagated mostly toward the northeast or southeast. From comparison with the E-region FAI occurrence, which is detected by a nearby VHF radar (31.57MHz), we found that AGW tended to propagate southeastward during FAI events. This result suggests that the interaction between AGW and E-region plasma plays an important role in generating FAI. Furthermore, polarization electric fields generated directly by AGW may contribute to the FAI generation. Keywords. Atmospheric composition and structure (Airglow and aurora), Ionosphere (Ionospheric irregularities, Mid-latitude ionosphere)

Highlights

Detailed structures of field-aligned irregularities (FAI) in the nighttime mid-latitude E-region were first investigated with the powerful middle and upper atmosphere (MU) radar at Shigaraki, Japan (34.9◦ N, 136.1◦ E) by Yamamoto et al (1991), who found two types of radar echoes: “quasiperiodic” echoes (QP echoes) and “continuous” echoes
We investigate, for the first time, relationships between the propagation direction of atmospheric gravity waves (AGW) in airglow images and the FAI occurrence observed simultaneously with a 31.57-MHz
Horizontal wavelength and horizontal wave velocity of the AGW during the Sporadic-E Experiment over Kyushu (SEEK)-2 campaign are consistent with the previous observation during the SEEK-1 campaign

Summary

Introduction

Detailed structures of field-aligned irregularities (FAI) in the nighttime mid-latitude E-region were first investigated with the powerful middle and upper atmosphere (MU) radar at Shigaraki, Japan (34.9◦ N, 136.1◦ E) by Yamamoto et al (1991), who found two types of radar echoes: “quasiperiodic” echoes (QP echoes) and “continuous” echoes. Onoma et al.: Relationship between AGW and FAI during SEEK-2 Latitude (deg.). 2002 23:56:31 LT Deviation (%) Longitude (deg.) Fig. 1. Map showing location of the all-sky imager (NishinoOmote) and VHF radar (Minamitane). Field-of-view of the all-sky imager with zenith angle less than 60◦ is shown by a circle (radius of 160 km). Area observed with the VHF radar is shown by the shaded area in the figure

Results

Discussion

Conclusion