scholarly journals Atmospheric Modes Excited by the 2021 August Eruption of the Fukutoku-okanoba Volcano, Izu-bonin Arc, Observed as Harmonic Oscillations of QZSS Total Electron Conte

Author(s):  
Kosuke Heki ◽  
Tatsuya Fujimoto

Abstract Continuous Plinian eruptions of volcanoes often excite atmospheric resonant oscillations with several distinct periods of a few minutes. We detected such harmonic oscillations excited by the 2021 August eruption of the Fukutoku-Okanoba volcano, a submarine volcano in the Izu-Bonin arc, in ionospheric total electron content (TEC) observed from global navigation satellite system (GNSS) stations deployed on three nearby islands, Chichijima, Hahajima, and Iwojima. Continuous records with the geostationary satellite of Quasi-Zenith Satellite System (QZSS) presented four frequency peaks of such atmospheric modes. The harmonic TEC oscillations, started at ~5:16 UT, exhibited an unprecedented large amplitude but decayed in a few hours.

2020 ◽  
Vol 38 (2) ◽  
pp. 347-357 ◽  
Author(s):  
Telmo dos Santos Klipp ◽  
Adriano Petry ◽  
Jonas Rodrigues de Souza ◽  
Eurico Rodrigues de Paula ◽  
Gabriel Sandim Falcão ◽  
...  

Abstract. In this work, a period of 2 years (2016–2017) of ionospheric total electron content (ITEC) from ionosondes operating in Brazil is compared to the International GNSS (Global Navigation Satellite System) Service (IGS) vertical total electron content (vTEC) data. Sounding instruments from the National Institute for Space Research (INPE) provided the ionograms used, which were filtered based on confidence score (CS) and C-Level flag evaluation. Differences between vTEC from IGS maps and ionosonde TEC were accumulated in terms of root mean squared error (RMSE). As expected, we noticed that the ITEC values provided by ionosondes are systematically underestimated, which is attributed to a limitation in the electron density modeling for the ionogram topside that considers a fixed scale height, which makes density values decay too rapidly above ∼800 km, while IGS takes in account electron density from GNSS stations up to the satellite network orbits. The topside density profiles covering the plasmasphere were re-modeled using two different approaches: an optimization of the adapted α-Chapman exponential decay that includes a transition function between the F2 layer and plasmasphere and a corrected version of the NeQuick topside formulation. The electron density integration height was extended to 20 000 km to compute TEC. Chapman parameters for the F2 layer were extracted from each ionogram, and the plasmaspheric scale height was set to 10 000 km. A criterion to optimize the proportionality coefficient used to calculate the plasmaspheric basis density was introduced in this work. The NeQuick variable scale height was calculated using empirical parameters determined with data from Swarm satellites. The mean RMSE for the whole period using adapted α-Chapman optimization reached a minimum of 5.32 TECU, that is, 23 % lower than initial ITEC errors, while for the NeQuick topside formulation the error was reduced by 27 %.


2021 ◽  
Author(s):  
Maria Kaselimi ◽  
Nikolaos Doulamis ◽  
Demitris Delikaraoglou

<p>Total Electron Content (TEC) is the integral of the location-dependent electron density along the signal path and is a crucial parameter that is often used to describe ionospheric variability, as it is strongly affected by solar activity. TEC is highly depended on local time, latitude, longitude, season, solar and geomagnetic conditions. The propagation of the signals from GNSS (Global Navigation Satellite System) throughout the ionosphere is strongly influenced by short- and long-term changes and ionospheric regular or irregular variations. <br>Long short-term memory network (LSTM) is a specific recurrent neural network architecture and is capable of learning time dependence in sequential problems and can successfully model ionosphere variability. As LSTM networks “memorize” long term correlations in a sequence, they can model complex sequences with various features, where solar radio flux at 10.7 cm and magnetic activity indices are taken into consideration to provide more accurate results. <br>Here, we propose a deep learning architecture to create regional TEC models around a station. The proposed model allows different solar and geomagnetic parameters to be inserted into the model as features. Our model has been evaluated under different solar and geomagnetic conditions. Also, the proposed model is tested for different time periods and seasonal variations and for varying geographic latitudes. </p>


2013 ◽  
Vol 19 (3) ◽  
pp. 374-390 ◽  
Author(s):  
Vinícius Amadeu Stuani Pereira ◽  
Paulo de Oliveira Camargo

As observáveis GNSS (Global Navigation Satellite System) são afetadas por erros sistemáticos devido aos elétrons livres presentes na ionosfera. O erro associado à ionosfera depende do Conteúdo Total de Elétrons (TEC - Total Electron Content), que é influenciado por diversas variáveis: ciclo solar, época do ano, hora local, localização geográfica e atividade geomagnética. Os receptores GPS (Global Positioning System), GLONASS (Global Orbiting Navigation Satellite System) e Galileo de dupla frequência permitem calcular o erro que afeta as observáveis GNSS e o TEC. Com a taxa de variação do TEC (ROT - Rate of TEC) pode-se determinar índices que indicam irregularidades da ionosfera, permitindo assim fazer inferências sobre o comportamento da mesma. Atualmente é possível realizar estudos dessa natureza no Brasil, devido às diversas Redes Ativas disponíveis, tais como a RBMC/RIBaC (Rede Brasileira de Monitoramento Contínuo/Rede INCRA de Bases Comunitárias) e a Rede GNSS Ativa do Estado de São Paulo. A pesquisa proposta visou à estimativa e análise de índices de irregularidades da ionosfera, além de suprir as geociências de informações sobre o comportamento da ionosfera.


2016 ◽  
Vol 6 (1) ◽  
pp. 56-60 ◽  
Author(s):  
V. Choliy

Random component of the total electron content (TEC) maps, produced by global navigation satellite system processing centres, was analysed. Helmert transform (HT) and two-dimension singular spectrum analysis (2dSSA) were used. Optimal parameters (in the sense calculation speed versus quality) of the 2dSSA windows were determined along with precision estimations.


2005 ◽  
Vol 23 (1) ◽  
pp. 183-189 ◽  
Author(s):  
J. Lilensten ◽  
Lj. R. Cander ◽  
M. T. Rietveld ◽  
P. S. Cannon ◽  
M. Barthélémy

Abstract. Space weather applications require real-time data and wide area observations from both ground- and space-based instrumentation. From space, the global navigation satellite system - GPS - is an important tool. From the ground the incoherent scatter (IS) radar technique permits a direct measurement up to the topside region, while ionosondes give good measurements of the lower part of the ionosphere. An important issue is the intercalibration of these various instruments. In this paper, we address the intercomparison of the EISCAT IS radar and two ionosondes located at Tromsø (Norway), at times when GPS measurements were also available. We show that even EISCAT data calibrated using ionosonde data can lead to different values of total electron content (TEC) when compared to that obtained from GPS.


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