• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.13-19
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• 2015

Plasma bubbles that occur in the equatorial F-region make up one of the most distinguishing phenomena in the ionosphere. Bubbles represent plasma depletions with respect to the background ionosphere, and are the major source of electron density irregularities in the equatorial F-region. Such bubbles are seen as plasma depletion holes (in situ satellite observations), vertical plumes (radar observations), and emission-depletion bands elongated in the north-south direction (optical observations). However, no technique can observe the whole three-dimensional structure of a bubble. Various aspects of bubbles identified using different techniques indicate that a bubble has a "shell" structure. This paper reviews the development of the concepts of "bubble" and "shell" in this context.

• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.133-140
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• 2002

Space Physics Sensor onboard the KOMPSAT-1, which was launched at 1999, had transmitted ionospheric data during the solar maximum from June 2000 to August 2001. When the KOMPSAT-1 has passed the equatorial region, equatorial bubbles, in which the electron density abruptly decreases, had frequently been detected. Statistical analysis of the data obtained during the entire operational period shows equatorial bubbles frequently occur across the Atlantic region where the geomagnetic field strength is weak. Also, equatorial bubbles occur more frequently for lower Kp index. The results are in good agreement with the previous observations by DMSP satellites and radio experiments at the Peruvian sector The correlation between electron density and the electron temperature shows various behaviors from event to event.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.38.3-39
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• 2009

Equatorial Plasma Bubble (herafter, EPB) is a common feature in low-latitude F-region during the night time. Since EPB causes significant impacts on the satellite communication and navigation systems, its accurate forecast is highly demanded by the GNSS users. Thus, further understanding of these features and their configuration is a challenging issue in space weather studies. The day-to-day variability of the plasma bubble activity was investigated by analyzing the TIMED/GUVI, ROCSAT-1, DMSP, and CHAMP satellite data. The pre-reversal enhancement (PRE) is known as the most important single parameter for the onset of plasma bubbles but we do not know yet to what extent the day-to-day variability of the bubble activity can be attributed to the PRE. We obtained the magnitude of the PRE from ROCSAT-1 and the occurrence of bubbles in relation to the PRE was investigated by using the coincident observations of EPBs from TIMED/GUVI, DMSP, and CHAMP. By conducting one-to-one comparison of the PRE characteristics with the EPB occurrence we examined the role of the PRE in the onset of EPBs.

• Journal of The Korean Astronomical Society
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• v.36 no.spc1
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• pp.109-115
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• 2003

We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.

• Journal of Astronomy and Space Sciences
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• v.39 no.2
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• pp.23-33
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• 2022

Electron density irregularities in the equatorial ionosphere at night are understood in terms of plasma bubbles, which are produced by the transport of low-density plasma from the bottomside of the F region to the topside. Equatorial plasma bubbles (EPBs) have been detected by various techniques on the ground and from space. One of the distinguishing characteristics of EPBs identified from long-term observations is the systematic seasonal and longitudinal variation of the EPB activity. Several hypotheses have been developed to explain the systematic EPB behavior, and now we have good knowledge about the key factors that determine the behavior. However, gaps in our understanding of the EPB climatology still remain primarily because we do not yet have the capability to observe seed perturbations and their growth simultaneously and globally. This paper reviews the occurrence climatology of EPBs identified from observations and the current understanding of its driving mechanisms.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.31-31
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• 2003

Equatorial Plasma Bubble(EPB)은 적도 지역에서 Rayleigh-Taylor Instability에 의해 발생하는 이온층 플라즈마의 불안정성 현상으로, 주변의 플라즈마 밀도에 비해 좁은 영역에서 플라즈마 밀도가 급격하게 떨어지는 현상을 말한다. 지역적으로 보면, 겨울철에는 대서양 지역에서 집중적으로 발생하고 여름철에서는 태평양 지역에서 많이 관측된다. 이러한 불안정 현상은 단파 통신 장애를 유발할 수 있기 때문에 많은 연구 대상이 되어왔지만, 아직까지 태양 활동이나 지자기 변화에 의한 상호 연관성이 규명되지 못 하고 있다. 이것은 Rayleigh-Taylor Instability를 발생시키는 여러 인자들이 매우 복잡하게 관련되어 있기 때문인데, 본 연구에서는 특정 지역에서 발생하는 EPB에 한정하여 태양 활동과의 상호 연관성에 대해 분석하고자 하였다. 또한 단순한 발생 빈도에 대한 통계적인 처리가 아닌, EPB하나 하나에 대한 특성을 분석함으로써 EPB의 발생과 관련한 보다 명확한 분석이 가능하게 되었다. 분석에 필요한 data는 KOMPSAT-1의 Langmuir Probe(LP)에 의해 2000년에서 2001년 사이에 얻은 이온층의 전자 밀도를 사용하였는데, KOMPSAT-1의 LP는 같은 기간 활동한 다른 위성에 비해 좋은 시간 분해능을 가지고 있기 때문에 EPB의 통계 처리에 적당한 것으로 생각되었다.

• Journal of Astronomy and Space Sciences
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• v.39 no.3
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• pp.87-98
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• 2022

The Far-UltraViolet (FUV) imager onboard the Ionospheric Connection Explorer (ICON) spacecraft provides two-dimensional limb images of oxygen airglow in the nightside low-latitude ionosphere that are used to determine the oxygen ion density. As yet, no FUV limb imager has been used for climatological analyses of Equatorial Plasma Bubbles (EPBs). To examine the potential of ICON/FUV for this purpose, we statistically investigate small-scale (~180 km) fluctuations of oxygen ion density in its limb images. The seasonal-longitudinal variations of the fluctuation level reasonably conform to the EPB statistics in existing literature. To further validate the ICON/FUV data quality, we also inspect climatology of the ambient (unfiltered) nightside oxygen ion density. The ambient density exhibits (1) the well-known zonal wavenumber-4 signatures in the Equatorial Ionization Anomaly (EIA) and (2) off-equatorial enhancement above the Caribbean, both of which agree with previous studies. Merits of ICON/FUV observations over other conventional data sets are discussed in this paper. Furthermore, we suggest possible directions of future work, e.g., synergy between ICON/FUV and the Global-scale Observations of the Limb and Disk (GOLD) mission.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.6_2
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• pp.607-613
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• 2012

Ionospheric anomaly is one of the major error sources which deteriorate the GNSS performance. In the equatorial region, effects of the ionospheric plasma bubbles are of great interest because they are pretty common phenomena, especially in the period of the high solar activity. In order to evaluate the GNSS performance under circumstance of the bubbles, an ionospheric scintillation monitor has been developed and installed in Bangkok, Thailand. Furthermore, a model simulating the ionospheric delay and scintillation due to the bubbles has been developed. Based on these developments, the effects of the simulated plasma bubbles are analyzed and their agreement with the real observation is demonstrated. An availability degradation of the GPS ground based augmentation system (GBAS) caused by the bubbles is exampled in details. Finally, an integrated GPS/INS approach based on the Doppler frequency is proposed to remedy the deterioration.

• Publications of The Korean Astronomical Society
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• v.15 no.spc2
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• pp.37-44
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• 2000

Two different types of plasma probes have been developed and are currently in operation on board the KOMPSAT-l. One is the cylindrical Langmuir Probe (LP) that measures the electron density and temperature from its current-voltage characteristics in thermal plasmas, and the other is the Electron Temperature Sensor (ETS) which directly gives the information of the ambient electron temperatures. These plasma probes provide the electron properties of the local nighttime ionosphere at the KOMPSAT-l altitudes. In this paper we briefly describe the probes and the initial results obtained from these probes since the beginning of their normal operation in April, 2000.