Study of structures of the sporadic E layer by using dense GNSS network observations

Saito, Susumu; Hosokawa, K.; Sakai, Jun; Tomizawa, Ichiro

doi:10.1002/navi.454

Cited by 9 publications

(8 citation statements)

References 20 publications

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“…ROTI values are estimated for each GPS satellite and GEONET receiver pairs and mapped at the IPPs at an altitude of 350 km. ROTI maps are generated every 5 min in near real-time with 2-min latency (Saito et al 2021).…”

Section: Methodsmentioning

confidence: 99%

Ionospheric disturbances observed over Japan following the eruption of Hunga Tonga-Hunga Ha’apai on 15 January 2022

Saito

2022

Earth Planets Space

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Traveling ionospheric disturbances (TIDs) were observed over Japan by using Global Navigation Satellite System (GNSS) receiver network data after the eruption of Hunga Tonga-Hunga Ha’apai in Tonga on 15 January 2022. Two types of TIDs with different characteristics were observed as perturbation in the total electron content (TEC). The first one arrived at Japan which are located about 7800 km away from Hunga Tonga-Hunga Ha’apai about 3 h after the eruption. The amplitude was about ± 0.5 TECU. The wavefronts was in the NNE–SSW direction and propagated in the WNW direction (– 69$$^\circ$$ ∘ counter-clockwise from the north) at 250 m s$$^{-1}$$ - 1 . The wavelength was estimated as 400 km. The second one arrived at Japan about 7 h after the eruption. The amplitude was about ± 1.0 TECU. The wavefronts was in the NE–SW direction and propagated in the NW direction (– 53$$^\circ$$ ∘ counter-clockwise from the north) at 270 m s$$^{-1}$$ - 1 . The wavelength was longer than the first one and was estimated as 800 km. The first one were associated with ionospheric irregularities represented by the rate of TEC index (ROTI). In contrast, the second one did not have irregularities all over the TIDs, but in only a limited region. The arrival of the first TID was too early for the atmospheric acoustic waves to arrive, while the arrival of the second TIDs approximately coincided with the arrival of surface pressure enhancement. To understand the mechanisms of the TIDs, further studies with wide-area observations as well as numerical calculations are necessary. TIDs and ionospheric irregularities after volcanic eruption could be threats to GNSS-based systems especially for those which utilize carrier-phase measurements. Graphical Abstract

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Section: Methodsmentioning

confidence: 99%

Ionospheric disturbances observed over Japan following the eruption of Hunga Tonga-Hunga Ha’apai on 15 January 2022

Saito

2022

Earth Planets Space

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“…Saito et al. (2021) showed that bottom side of the front‐like Es layer appeared to have wavy structure which is steep on the front side and gentle in the tail side by network observations of the total electron content and its fluctuation.…”

Section: Discussionmentioning

confidence: 99%

“…However, other causes of fluctuations in propagation path such as tropospheric refractivity variation should also be examined. Statistical analysis of the EsAP of the ILS LOC signals and comparison with other observations such as GNSS network observation (Saito et al., 2021) and EsAP network observation (Hosokawa et al., 2021) and with numerical simulation (Andoh et al., 2020) are necessary and left for future studies.…”

Section: Discussionmentioning

confidence: 99%

“…However, one should be careful in interpreting the behavior of the deviation angle, because the deviation output goes to zero, when the signal power is low and the difference between the amplitudes of signals modulated at 90 (Saito et al, 2021) and EsAP network observation (Hosokawa et al, 2021) and with numerical simulation (Andoh et al, 2020) are necessary and left for future studies.…”

Section: Possible Detection Of Es Layer Structurementioning

confidence: 99%

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Anomalous Long‐Distance Propagation of ILS LOC Signals by the Es Layer and Its Impact on Aviation Receivers

Saito,

Hosokawa,

Sakai

et al. 2023

Space Weather

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Anomalous long‐distance propagation of Very High Frequency radio waves of aeronautical navigation systems was investigated by an airborne Instrument Landing System (ILS) localizer (ILS LOC) receiver installed on the ground at Kure, Japan (34.245°N, 132.528°E). Intense ILS LOC type signals were observed and the received power was strong enough for the aviation receiver to output course deviation. The radio source was identified by receiving the Morse Code for identification as the localizer‐type directional aid (LDA) serving the Runway‐21 of the Hualien Airport, Taiwan (24.0396°N, 121.6221°E) of which beam pointed close to the receiver. This result supports that the source of the signals often observed at the same frequency at the same location is most probably the LDA at the Hualien Airport. The maximum received power was −99 dBm for an omni‐directional antenna. It was strong enough to cause co‐channel interference. Considering stronger power (−70 dBm) found in previous observations at the same frequency at the same location, anomalous propagation of ILS LOC signals by the Es layer could be a cause of interference when a receiver was near the center of the ILS LOC beam. The course deviation output was consistent with the geometry between the beam of Runway‐21 LDA at the Hualien Airport and the receiver. However, the observed course deviation fluctuated remarkably even when the received power was strong enough. The fluctuation of the course deviation may indicate the structure of the Es layer, and observation of the course deviation could be used to diagnose the Es layer structure.

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“…RO-observed Es layers from COSMIC and Fengyun-3C (FY-3C) missions were intercompared globally and found to be consistent, though, with slight differences (Xu et al 2022). In addition, Saito et al (2021) identified fine structures (such as the sub-structures in the Es layer front) by utilizing total electron content (TEC) index (ROTI) maps with dense Global Navigation Satellite System (GNSS) observations over Japan.…”

Section: Introductionmentioning

confidence: 99%

Occurrence features of intermediate descending layer and Sporadic E observed over the higher mid-latitude ionospheric station of Moscow

Oikonomou

Leontiou

Haralambous

et al. 2023

Earth Planets Space

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Nine years of ionograms from a higher mid-latitude ionospheric station (Moscow) are analyzed, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs). Es and IDL traces are observed over Moscow, which are characterized by a 12-h periodicity prevailing throughout the year. Shorter periodicities in IDL and Es occurrence are also observed. A 6-h periodicity in Es and IDL dominates during November and December, while an 8-h periodicity is found mainly from October to February for IDL and in July for Es. These periodicities are primarily induced by the semi-, quarter- and terdiurnal thermospheric tides, respectively. Our results also establish the systematic and widespread manifestation of shorter-scale (4.8- and 4-h) periodicities observed mainly for IDL and less frequently for Es only during December and January, in the nine years considered, which is most probably linked to higher-order solar tides. Graphical Abstract

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Study of structures of the sporadic E layer by using dense GNSS network observations

Cited by 9 publications

References 20 publications

Ionospheric disturbances observed over Japan following the eruption of Hunga Tonga-Hunga Ha’apai on 15 January 2022

Ionospheric disturbances observed over Japan following the eruption of Hunga Tonga-Hunga Ha’apai on 15 January 2022

Anomalous Long‐Distance Propagation of ILS LOC Signals by the Es Layer and Its Impact on Aviation Receivers

Occurrence features of intermediate descending layer and Sporadic E observed over the higher mid-latitude ionospheric station of Moscow

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