National Repository of Grey Literature 6 records found  Search took 0.01 seconds. 
Propagation of very low frequency radio waves in the Earth-ionosphere waveguide
Guth Jarkovský, Jiří ; Santolík, Ondřej (advisor) ; Píša, David (referee)
Bleskové výboje jsou zdrojem silného elektromagnetického (EM) záření, především v oblasti velmi nízkých frekvencí (VLF) 3-30 kHz. Toto záření se vlnovodem mezi Zemí a spodní vrstvou ionosféry dokáže došířit až do vzdálenosti tisíců kilometrů od zdrojového blesku. Pomocí měření vhodných komponent EM pole je možné určit směr, odkud EM vlna vy- volaná bleskem přišla. Výsledkem této práce je algoritmus, který daný výpočet provede, otestovaný na datech z měřící stanice umístěné v jižní Francii. Algoritmus byl testován jednak na jednotlivé bleskové výboje se známými polohami a jednak na signál z vysílačů určených ke komunikaci s ponorkami, neboť tyto vysílají ve stejném pásmu a jsou též vhodné pro aplikaci nově vyvinutého algoritmu. 1
Study of electromagnetic emissions recorded by the DEMETER satellite
Píša, David
David PÍŠA Study of electromagnetic emissions recorded by the DEMETER satellite Abstract : This thesis presents results based on wave measurements performed by the DEMETER space- craft. This French spacecraft was operating between 2004 and 2010 at the altitude of ∼660 km. We focus on measurements of the electromagnetic waves and plasma density in the vicinity of imminent earthquakes. In the first part, we present a study of plasma density variations in the vicinity of a very powerful earthquake in Chile (Mw 8.8) which occurred on February 27, 2010. Data recorded before the main shock along orbits close to the future epicenter showed increasing plasma den- sities. A statistical analysis using 4 years of data to monitor density variations under similar conditions has been performed. This study shows that a large increase of the plasma density is very uncommon at this location. In the second part, a statistical study (∼6.5 years) of variations of VLF wave intensity is shown. We have analyzed all available data measured close (in time and space) to large earth- quakes (M≥5). Data related to more than 12000 earthquakes have been compared with an unperturbed background distribution. We confirm the previously reported results of a statis- tically significant decrease of the wave intensity at frequencies of about...
Studium elektromagnetických emisí pozorovaných družicí DEMETER
Píša, David ; Santolík, Ondřej (advisor) ; Shklyar, David R. (referee) ; Souček, Jan (referee)
David PÍŠA Study of electromagnetic emissions recorded by the DEMETER satellite Abstract : This thesis presents results based on wave measurements performed by the DEMETER space- craft. This French spacecraft was operating between 2004 and 2010 at the altitude of ∼660 km. We focus on measurements of the electromagnetic waves and plasma density in the vicinity of imminent earthquakes. In the first part, we present a study of plasma density variations in the vicinity of a very powerful earthquake in Chile (Mw 8.8) which occurred on February 27, 2010. Data recorded before the main shock along orbits close to the future epicenter showed increasing plasma den- sities. A statistical analysis using 4 years of data to monitor density variations under similar conditions has been performed. This study shows that a large increase of the plasma density is very uncommon at this location. In the second part, a statistical study (∼6.5 years) of variations of VLF wave intensity is shown. We have analyzed all available data measured close (in time and space) to large earth- quakes (M≥5). Data related to more than 12000 earthquakes have been compared with an unperturbed background distribution. We confirm the previously reported results of a statis- tically significant decrease of the wave intensity at frequencies of about...
Statistical Study of the Ionospheric Density Variation Related to the 2010 Chile Earthquake and Measured by the DEMETER Satellite
Píša, David ; Santolík, Ondřej ; Parrot, M.
Statistical Study of the Ionospheric Density Variation Related to the 2010 Chile Earthquake and Measured by the DEMETER Satellite.

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