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Simulations of spacecraft measurements of electromagnetic waves in the Earth's magnetosphere
Hanzelka, Miroslav ; Santolík, Ondřej (advisor) ; Kolmašová, Ivana (referee)
For more than fifty years simulations of electromagnetic (EM) wave propa- gation are used to study the Earth's magnetosphere and to analyze EM emissions observed by spacecraft. In this work we focus on the propagation of EM waves in the frequency range from 100 Hz to 10 000 Hz within the region of the inner magnetosphere. We use a numerical procedure which performs ray tracing simu- lations and finds the wave trajectory along with other wave properties. Using these simulations we study propagation properties of equatorial noise emissions. Another subject of this work is development of a propagation scheme explaining a conjugate observation of quasiperiodic emissions by the Van Allen Probe A (VAP-A) spacecraft and the ground station in Athabasca. In this case we make use of a density distribution model based on measurements of plasmaspheric electron density done by the EMFISIS instrument onboard VAP-A. 1
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Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere
Záhlava, Jan ; Němec, František (advisor) ; Chum, Jaroslav (referee) ; Manninen, Jyrki (referee)
Title: Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere Author: Jan Záhlava Department: Department of Surface and Plasma Physics Supervisor: doc. RNDr. František Němec, PhD., Department of Surface and Plasma Physics Abstract: The thesis focuses on lightning-related electromagnetic wave phenomena observed by spacecraft in the Earth's inner magnetosphere. Two different approaches are used to identify the frequency and spatial extent where lightning generated emissions significantly contribute to the overall wave intensity. First, whistler detections onboard the DEMETER spacecraft are used to sort the measurements according to the whistler activity. Second, we use a geographic distribution of lightning activity and analyze a dependence of the overall wave intensity on geomagnetic longitude. We show that, especially during the night, the overall wave intensity observed in the plasmasphere is well correlated with lightning activity. The other focus of the study is on special electromagnetic wave events consisting of alternating frequency bands of enhanced and reduced wave intensity formed in the ionosphere due to lightning. We analyze their occurrence and parameters, and we suggest a possible mechanism of their formation. Keywords: lightning, waves in plasma, whistlers, plasmasphere
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Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere
Záhlava, Jan ; Němec, František (advisor)
Title: Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere Author: Jan Záhlava Department: Department of Surface and Plasma Physics Supervisor: doc. RNDr. František Němec, PhD., Department of Surface and Plasma Physics Abstract: The thesis focuses on lightning-related electromagnetic wave phenomena observed by spacecraft in the Earth's inner magnetosphere. Two different approaches are used to identify the frequency and spatial extent where lightning generated emissions significantly contribute to the overall wave intensity. First, whistler detections onboard the DEMETER spacecraft are used to sort the measurements according to the whistler activity. Second, we use a geographic distribution of lightning activity and analyze a dependence of the overall wave intensity on geomagnetic longitude. We show that, especially during the night, the overall wave intensity observed in the plasmasphere is well correlated with lightning activity. The other focus of the study is on special electromagnetic wave events consisting of alternating frequency bands of enhanced and reduced wave intensity formed in the ionosphere due to lightning. We analyze their occurrence and parameters, and we suggest a possible mechanism of their formation. Keywords: lightning, waves in plasma, whistlers, plasmasphere
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Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere
Záhlava, Jan ; Němec, František (advisor)
Title: Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere Author: Jan Záhlava Department: Department of Surface and Plasma Physics Supervisor: doc. RNDr. František Němec, PhD., Department of Surface and Plasma Physics Abstract: The thesis focuses on lightning-related electromagnetic wave phenomena observed by spacecraft in the Earth's inner magnetosphere. Two different approaches are used to identify the frequency and spatial extent where lightning generated emissions significantly contribute to the overall wave intensity. First, whistler detections onboard the DEMETER spacecraft are used to sort the measurements according to the whistler activity. Second, we use a geographic distribution of lightning activity and analyze a dependence of the overall wave intensity on geomagnetic longitude. We show that, especially during the night, the overall wave intensity observed in the plasmasphere is well correlated with lightning activity. The other focus of the study is on special electromagnetic wave events consisting of alternating frequency bands of enhanced and reduced wave intensity formed in the ionosphere due to lightning. We analyze their occurrence and parameters, and we suggest a possible mechanism of their formation. Keywords: lightning, waves in plasma, whistlers, plasmasphere
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Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere
Záhlava, Jan ; Němec, František (advisor) ; Chum, Jaroslav (referee) ; Manninen, Jyrki (referee)
Title: Lightning-Related Electromagnetic Wave Phenomena in the Earth's Magnetosphere Author: Jan Záhlava Department: Department of Surface and Plasma Physics Supervisor: doc. RNDr. František Němec, PhD., Department of Surface and Plasma Physics Abstract: The thesis focuses on lightning-related electromagnetic wave phenomena observed by spacecraft in the Earth's inner magnetosphere. Two different approaches are used to identify the frequency and spatial extent where lightning generated emissions significantly contribute to the overall wave intensity. First, whistler detections onboard the DEMETER spacecraft are used to sort the measurements according to the whistler activity. Second, we use a geographic distribution of lightning activity and analyze a dependence of the overall wave intensity on geomagnetic longitude. We show that, especially during the night, the overall wave intensity observed in the plasmasphere is well correlated with lightning activity. The other focus of the study is on special electromagnetic wave events consisting of alternating frequency bands of enhanced and reduced wave intensity formed in the ionosphere due to lightning. We analyze their occurrence and parameters, and we suggest a possible mechanism of their formation. Keywords: lightning, waves in plasma, whistlers, plasmasphere
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Propagation of very low frequency radio waves in the Earth-ionosphere waveguide
Guth Jarkovský, Jiří ; Santolík, Ondřej (advisor) ; Píša, David (referee)
Lightning strokes emit strong electromagnetic (EM) radiation, mostly in the very low frequency band (VLF) 3-30 kHz. This radiation propagates in the Earth-ionosphere wa- veguide across distances of thousands of kilometres. Using measurements of several com- ponents of the EM feld, it is possible to determine the direction of arrival of an EM wave. The main result of this thesis is an algorithm for this analysis and its application to data measured by a station located in southern France. The algorithm was used to determine the direction of arrival of signal from several lightning strokes with known locations as well as from emitters used for submarine communication, as those also emit waves in the VLF band and thus are also suitable for application of the algorithm. 1
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Selected Wave Phenomena in the Earth's Magnetosphere
Bezděková, Barbora ; Němec, František (advisor) ; Macúšová, Eva (referee)
Electromagnetic waves are crucial for energy transfer in the nearly collision- less plasma of the Earth's inner magnetosphere. The waves in the frequency range 1-8 kHz whose visualisation in the form of frequency-time spectrograms reveals a harmonic frequency modulation of the wave intensity are called magnetospheric line radiation (MLR). Waves characterized by a nearly periodic time modulation of the wave intensity observed at frequencies between about 0.5 and 4 kHz are called quasiperiodic (QP) emissions. Although both types of the events were re- peatedly observed by ground-based instruments and low-altitude satellites, their origin remains still unclear. Between 2004 and 2010 these wave events were me- asured by the DEMETER spacecraft (almost Sun-synchronous orbit, altitude of about 700 km). This thesis presents a systematic study of the properties of the observed events, a comparison of the observations by the spacecraft and ground- based instruments, and an investigation of a relation to solar wind parameters.
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Simulations of spacecraft measurements of electromagnetic waves in the Earth's magnetosphere
Hanzelka, Miroslav ; Santolík, Ondřej (advisor) ; Kolmašová, Ivana (referee)
For more than fifty years simulations of electromagnetic (EM) wave propa- gation are used to study the Earth's magnetosphere and to analyze EM emissions observed by spacecraft. In this work we focus on the propagation of EM waves in the frequency range from 100 Hz to 10 000 Hz within the region of the inner magnetosphere. We use a numerical procedure which performs ray tracing simu- lations and finds the wave trajectory along with other wave properties. Using these simulations we study propagation properties of equatorial noise emissions. Another subject of this work is development of a propagation scheme explaining a conjugate observation of quasiperiodic emissions by the Van Allen Probe A (VAP-A) spacecraft and the ground station in Athabasca. In this case we make use of a density distribution model based on measurements of plasmaspheric electron density done by the EMFISIS instrument onboard VAP-A. 1
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Investigation of lightning-generated elecromagnetic waves in a broad frequency range
Fišer, Jiří ; Santolík, Ondřej (advisor) ; Němec, František (referee)
In this work I present a study dedicated to the penetration of whistler- mode waves to the ionosphere. An algorithm of automatic detection of whist- lers in spectrograms computed from the data measured on the DEMETER sa- tellite is described. A method of causative lightning detected by the EUCLID lightning detection network assignment to a detected whistlers is described. Results of statistical study dedicated to relationship between the detected whistlers and assigned causative lightning. Based on the proccessing of data from 364 passes of the DEMETER satellite over monitored area is shown, that mean whistler amplitude decreases with distance between the causative lightning, increses with causative lightning current and in the evening is ap- proximately three times higher than in the morning. A study dedicated to subprotonospheric whistlers is presented. We found, that subprotonospheric whistler causative lightnings currents are very high compared to that of usual 0+ whistlers.
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