Observations of small‐ to large‐scale ionospheric irregularities associated with plasma bubbles with a transequatorial HF propagation experiment and spaced GPS receivers

Saito, Susumu; Maruyama, Takashi; Ishii, Mamoru; Kubota, Minoru; Ma, Guanyi; Chen, Yanhong; Li, Jinghua; Duyen, C. Ha; Truong, Thanh Le

doi:10.1029/2008ja013149

Cited by 13 publications

(11 citation statements)

References 13 publications

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“…Maruyama and Kawamura (2006) observed HF-TEP from Australia to Japan and showed that directions of arrival (DOAs; azimuth and elevation angles) measurements of transequatorial propagating HF radio waves enables us to monitor the existence of plasma Radio Science 10.1029/2017RS006518 bubbles as well as to estimate their drift velocity. Saito et al (2008) showed that the drift velocities estimated by the HF-TEP DOA measurements were consistent with plasma bubble drift velocities estimated by GPS measurements for their data set obtained in 1 month. However, Tsunoda et al (2016a) pointed out that abnormally fast velocities were sometimes obtained from the HF-TEP DOA measurements.…”

Section: Introductionsupporting

confidence: 80%

Arrival Angle and Travel Time Measurements of HF Transequatorial Propagation for Plasma Bubble Monitoring

2018

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A system to measure travel times of high‐frequency (HF) radio waves was developed based on a digital receiver technique. Travel times of HF transequatorial propagation (HF‐TEP) of signals of Radio Australia from Shepparton (36.2°S, 145.3°E), Australia to Oarai (36.3°N, 140.6°E), Japan, were measured by the system. Directions of arrival of the signals were simultaneously observed by a HF Direction Finder located at Oarai (Oarai Direction Finder: ODF). When the ODF observed signals arriving from great circle direction, constant multiple discrete values of propagation times were observed. After sunset, propagation times longer than those expected from the great circle propagation were observed and the ODF observed corresponding signals from off‐great‐circle directions (off‐great‐circle propagation). The observed maximum azimuth angle deviation (∼50°) was much larger than the angle that would have been obtained when a single side reflection in HF‐TEP was assumed. This result supports the multireflection model of off‐great‐circle propagation of HF‐TEP proposed by Tsunoda et al. (2016a, https://doi.org/10.1002/2015JA021695). The propagation time measurements are useful to determine the propagation paths, when they are used with HF‐TEP observations by a HF Direction Finder system. Ray tracing analysis with the propagation times and arrival angles will contribute to monitoring locations of plasma bubbles as well as understanding their structures and the physics behind them. The technique can also be applied to determine the propagation paths in the normal great circle propagations and other geophysical phenomena, such as midlatitude trough, deep traveling ionospheric disturbance modulation of the ionospheric height due to Perkins instability and sporadic E layer irregularities.

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Section: Introductionsupporting

confidence: 80%

Arrival Angle and Travel Time Measurements of HF Transequatorial Propagation for Plasma Bubble Monitoring

2018

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“…For example, the lengths of great-circle TEP paths (1) from Tsumeb (19.3°S, 17.7°E) to Lindau (51.4°N, 10.1°E) (Röttger 1973), and (2) from Shepparton (36.2°S, 135.3°E) to Oarai (36.3°N, 140.6°E) (Maruyama and Kawamura 2006;Saito et al 2008), were both about 8,000 km. With this viewing geometry, signals that arrive at azimuths ±60°a way from the great-circle path have been detected.…”

Section: Transequatorial Propagation Resultsmentioning

confidence: 99%

Upwelling: a unit of disturbance in equatorial spread F

Tsunoda

2015

Prog. in Earth and Planet. Sci.

120

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Plasma structure in the nighttime equatorial F layer, often referred to as equatorial spread F (ESF), is not uniformly distributed, either in time or in space. Observations indicate that ESF in the bottomside F layer takes the form of patches; plasma structure within the F layer takes the form of localized plasma depletions, called equatorial plasma bubbles (EPBs), which tend to occur in clusters. Another observed feature is an upwelling, which has been described as a localized, upward modulation of isodensity contours in the bottomside F layer. Interestingly, zonal widths of ESF patches, EPB clusters, and upwellings are similar. Moreover, all display an east-west asymmetry. The objective of this paper is to show, for the first time, that an ESF patch is the bottomside counterpart of an EPB cluster, and that both are products of the electrodynamical process that takes place within an upwelling. The process can be described as having three phases: (1) amplification of upwelling amplitude during the post-sunset rise of the F layer, (2) launching of the first EPB of the evening, from crest of the upwelling, and (3) structuring of plasma within the upwelling. Hence, an upwelling, whose presence is responsible for the formation of ESF patches and EPB clusters, can be envisioned as a unit of disturbance that occurs in the nighttime equatorial ionosphere.

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“…The correlation is better near the magnetic equator than near the crests. The previous studies showed that the scintillation occurrence in the low-latitude region is almost associated with plasma bubble (Rama Rao et al, 2006;Saito et al, 2008;Abadi et al, 2014;Bhattacharyya et al, 2014). The scintillations are due to ionospheric irregularities generated at the equatorial region through RT plasma instability, which is considered as the primary mechanism responsible for the generation of plasma bubble.…”

Section: Scintillation Climatology In the Vietnam Regionmentioning

confidence: 99%

Climatology of ionospheric scintillation over the Vietnam low-latitude region for the period 2006–2014

Lân

Minh

Amory‐Mazaudier

et al. 2017

Advances in Space Research

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This paper presents the characteristics of the occurrence of ionospheric scintillations at low-latitude, over Vietnam, by using continuous data of three GSV4004 receivers located at PHUT/Hanoï (105.9 o E, 21.0 o N; magnetic latitude 14.4 o N), HUES/Hue (107.6 o E, 16.5 o N; magnetic latitude 9.5 o N) and HOCM/ Ho Chi Minh city (106.6 o E, 10.8 o N; magnetic latitude 3.3 o N) for the period 2006-2014. The results show that the scintillation activity is maximum during equinox months for all the years and depends on solar activity as expected. The correlations between the monthly percentage scintillation occurrence and the F10.7 flux are of 0.40, 0.52 and 0.67 for PHUT, HUES and HOCM respectively. The distribution of scintillation occurrences is dominant in the pre-midnight sector and around the northern crest of the equatorial ionization anomaly (EIA), from the 15 o N to 20 o N geographic latitude with a maximum at 16 o N. The results obtained from the directional analysis show higher distributions of scintillations in the southern sky of PHUT and in the northern sky of HUES and HOCM, and in the elevation angles smaller than 40 o. The correlation between ROTI and S 4 is low and 2 rather good at PHUT (under EIA) than HOCM (near equator). We found better correlation in the post-midnight hours and less correlation in the pre-midnight hours for all stations. When all satellites are considered during the period of 2009-2011, the range of variation of the ration between ROTI and S 4

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Observations of small‐ to large‐scale ionospheric irregularities associated with plasma bubbles with a transequatorial HF propagation experiment and spaced GPS receivers

Cited by 13 publications

References 13 publications

Arrival Angle and Travel Time Measurements of HF Transequatorial Propagation for Plasma Bubble Monitoring

Arrival Angle and Travel Time Measurements of HF Transequatorial Propagation for Plasma Bubble Monitoring

Upwelling: a unit of disturbance in equatorial spread F

Climatology of ionospheric scintillation over the Vietnam low-latitude region for the period 2006–2014

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