Time evolution of high-altitude plasma bubbles imaged at geomagnetic conjugate points

K Shiokawa,T Ogawa,Y Otsuka,P Wilkinson

doi:10.5194/angeo-22-3137-2004

K Shiokawa, T Ogawa + Show 2 more

Open Access

https://doi.org/10.5194/angeo-22-3137-2004

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Journal: Annales Geophysicae	Publication Date: Sep 23, 2004
Citations: 72	License type: CC BY 3.0

Affiliation: Nagoya University, Services Australia

Abstract

Abstract. Temporal and spatial evolution of two high-altitude plasma bubbles (evening and midnight) was observed on 4 April 2002, at geomagnetic conjugate points at Sata, Japan (magnetic latitude 24° N), and Darwin, Australia (magnetic latitude 22° S), using two 630-nm airglow imagers. The apex height of the bubbles reached ~1500km. The upward velocity of the evolution was faster in the evening (~170m/s at 20:00-21:00 LT) than around midnight (~28m/s at 23:00-00:00 LT). Bifurcating features of the bubbles into a smaller scale size of ~50km were clearly seen for both the evening and midnight bubbles, showing fairly good conjugacy between the Northern and Southern Hemispheres.

Highlights

Equatorial plasma bubble is commonly seen in the postsunset equatorial latitudes as a result of the Rayleigh-Taylor instability, where the low-density plasma on the bottomside of the equatorial ionosphere penetrates through the dense F -layer by polarization electric field (Kelley, 1989)
Kelley et al (2002) showed spectacular high-altitude plasma bubbles seen in the airglow images at Haleakala, Hawaii (20.7◦ N, 203.8◦ E; geomagnetic latitude: 21◦ N, dip angle: 37◦)
We report time evolution of high-altitude plasma bubbles observed on 4 April 2002, at geomagnetic conjugate points at Sata and Darwin

Summary

Introduction

Equatorial plasma bubble is commonly seen in the postsunset equatorial latitudes as a result of the Rayleigh-Taylor instability, where the low-density plasma on the bottomside of the equatorial ionosphere penetrates through the dense F -layer by polarization electric field (Kelley, 1989). The bubbles, which are recognized as equatorial spread-F on ionograms, have initially been detected by radio-sounding techniques On the other hand, is a powerful tool to detect spatial and temporal evolution of the bubble structures from ground and satellite We report time evolution of high-altitude plasma bubbles observed on 4 April 2002, at geomagnetic conjugate points at Sata and Darwin. Poleward growth and bifurcation of the bubbles were observed in the field-of-view of all-sky airglow imagers both in the evening (21:00 LT) and around midnight

Observation

Discussion

Conclusion