Determining spatio-temporal characteristics of coseismic travelling ionospheric disturbances (CTID) in near real-time

Earthquakes are known to generate ionospheric disturbances that are commonly referred to as co-seismic travelling ionospheric disturbances (CTID). In this work, for the first time, we present a novel method that enables to automatically detect CTID in ionospheric GNSS-data, and to determine their spatio-temporal characteristics (velocity and azimuth of propagation) in near-real time (NRT), i.e., less than 15 min after an earthquake. The obtained instantaneous velocities allow us to understand the evolution of CTID and to estimate the location of the CTID source in NRT. Furthermore, also for the first time, we developed a concept of real-time travel-time diagrams that aid to verify the correlation with the source and to estimate additionally the propagation speed of the observed CTID. We apply our methods to the Mw7.4 Sanriku earthquake of 09/03/2011 and the Mw9.0 Tohoku earthquake of 11/03/2011, and we make a NRT analysis of the dynamics of CTID driven by these seismic events. We show that the best results are achieved with high-rate 1 Hz data. While the first tests are made on CTID, our method is also applicable for detection and determining of spatio-temporal characteristics of other travelling ionospheric disturbances that often occur in the ionosphere driven by many geophysical phenomena.

Properties and Generation of Large Scale Travelling Ionospheric Disturbances during 8 September 2017

<p>Large Scale Travelling Ionospheric Disturbances (LSTIDs) are a frequent phenomenon during ionospheric storms, indicating strong electrodynamic processes in high latitudes. LSTIDs are signatures of Atmospheric Gravity Waves (AGW) observed in the changes of the electron density in the ionosphere. During ionospheric storms, large scale AGWs are often generated in the vicinity of the auroral region, where sudden strong heating processes take place.</p><p>Many LSTIDs are observed during the ionosphere storm during the September 2017 Space Weather event. In this presentation, the LSTID occurrence on 8<sup>th</sup> September 2017 is analysed in more detail, based on a TID detection method using ground based Global Navigation Satellite System (GNSS) measurements. Fast LSTIDs are observed in midlatitudes between 0-3 UT and 13-16 UT. Slow LSTIDs are observed between 3-12 UT. A significant strong wave-like TEC perturbation occurred in high latitudes at noon, which vanished at around 50°N. A strong single LSTID in mid-latitudes generated in high latitudes around 18 UT. Consulting IMAGE magnetometer data, ionosonde measurements and Swarm field aligned current measurements, strong heating processes, the extension of the Auroral oval and unusual electrodynamic processes are discussed as source mechanisms for these LSTIDs.</p>

An overview of methodologies for real-time detection, characterisation and tracking of traveling ionospheric disturbances developed in the TechTIDE project

The main objective of the TechTIDE project (warning and mitigation technologies for travelling ionospheric disturbances effects) is the development of an identification and tracking system for travelling ionospheric disturbances (TIDs) which will issue warnings of electron density perturbations over large world regions. The TechTIDE project has put in operation a real-time warning system that provides the results of complementary TID detection methodologies and many potential drivers to help users assess the risks and develop mitigation techniques tailored to their applications. The TechTIDE methodologies are able to detect in real time activity caused by both large-scale and medium-scale TIDs and characterize background conditions and external drivers, as an additional information required by the users to assess the criticality of the ongoing disturbances in real time. TechTIDE methodologies are based on the exploitation of data collected in real time from Digisondes, Global Navigation Satellite System (GNSS) receivers and Continuous Doppler Sounding System (CDSS) networks. The results are obtained and provided to users in real time. The paper presents the achievements of the project and discusses the challenges faced in the development of the final TechTIDE warning system.

POSSÍVEL TID GERADO NA REGIÃO POLAR E OBSERVADO SOBRE ESTAÇÕES EQUATORIAIS E DE BAIXAS LATITUDES

Os Distúrbios Ionosféricos Propagantes (TID’s - Travelling Ionospheric Disturbances) são irregularidades no plasma ionosférico que se propagam com velocidades da ordem de dezenas a poucas centenas de quilômetros por hora. Nesse trabalho, foram detectadas e caracterizadas perturbações do tipo LSTID’s (Large scale Travelling Ionospheric Disturbances), em baixas latitudes, durante intensas tempestades geomagnéticas e também a forma como se propagação. Utilizou-se registros ionosféricos obtidos a partir de digissondas do tipo CADI (Canadian Advanced Digital Ionosonde) localizada na cidade de Natal e do tipo DSP (Digisonde Portable Souder) localizadas nas cidades de Cachoeira Paulista, Ramey e Eglin. Os dados de sondagem de Ramey e Eglin foram disponibilizados pela Global Ionosphere Radio Observatory (GIRO). Para observar os efeitos de tempestades sobre a ionosfera polar, foram utilizadas imagens aurorais do polo Norte, obtidas pelo satélite POLAR, que mostraram a intensificação do eletrojato auroral pela injeção de partículas nas cúspides. O período analisado compreendeu os dias 06 e 07 de abril de 2000 e os índices utilizados para caracterizar a atividade magnética nesse período foram Dst, Kp, e AE, além da componente Bz do campo magnético interplanetário. A tempestade ocorrida no dia 6 de abril apresentou um Dstmin = - 288 nT. A partir de gráficos de isolinhas foram verificados comportamentos anômalos da ionosfera sobre as quatro cidades, caracterizando a propagação como sendo do tipo LSTID’s, gerados pela expansão do oval auroral nos polos.