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Analysis of propagation of "lion roar" emissions using the data of the Cluster spacecraft
Krupař, Vratislav ; Santolík, Ondřej (advisor) ; Souček, Jan (referee)
The main task of this thesis was a statistical study of lion roar wave emissions in the Earth's magnetosheath. Large data set obtained from the Cluster spacecraft has been used. We have studied a frequency distribution, a wave power distribution and a spatial distribution. We have investigated propagation characteristics using advanced methods applied on multi-components measurement. We have confirmed the narrow-band structure of lion roars. We have compared observed and estimated (from the cold plasma theory) time lags between spacecraft during short separations.
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Stereoscopic Observations of Solar Radio Emissions by the S/WavesInstrument onboard the STEREO Spacecraft
Krupař, Vratislav ; Santolík, Ondřej (advisor) ; Krucker, Samuel (referee) ; Wimmer-Schweingruber, Robert F. (referee)
This PhD thesis is primarily dedicated to a study of type III radio bursts observed by the S/Waves instrument onboard Solar TErrestrial RElations Observatory (STEREO). These emissions are produced by beams of suprathermal electrons escaping the corona along open magnetic field lines during increased solar activity. As fast electrons propagate in the interplanetary (IP) medium, Langmuir waves are generated at the local electron plasma frequency fpe by a bump-on-tail instability and can be afterwards converted by a non-linear process into radio emissions at fpe and/or 2fpe: type III radio bursts. We have developed a goniopolarimetric (GP, also referred to as direction-finding) inversion using the Singular Value Decomposition (SVD) technique for electric measurements on three non-orthogonal antennas. It allows us to retrieve both wave vector directions and polarization properties of incident waves. We have also investigated the influence of extended sources (as a typical feature of type III radio bursts) on measured spectral matrices. We have found an empirical relation between apparent source sizes and spectral matrices decomposed by SVD. Abovementioned techniques have been extensively tested on data obtained by the High Frequency Receiver (HFR, a part of S/Waves). We have performed statistical analysis of a...
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Stereoscopic Observations of Solar Radio Emissions by the S/WavesInstrument onboard the STEREO Spacecraft
Krupař, Vratislav
This PhD thesis is primarily dedicated to a study of type III radio bursts observed by the S/Waves instrument onboard Solar TErrestrial RElations Observatory (STEREO). These emissions are produced by beams of suprathermal electrons escaping the corona along open magnetic field lines during increased solar activity. As fast electrons propagate in the interplanetary (IP) medium, Langmuir waves are generated at the local electron plasma frequency fpe by a bump-on-tail instability and can be afterwards converted by a non-linear process into radio emissions at fpe and/or 2fpe: type III radio bursts. We have developed a goniopolarimetric (GP, also referred to as direction-finding) inversion using the Singular Value Decomposition (SVD) technique for electric measurements on three non-orthogonal antennas. It allows us to retrieve both wave vector directions and polarization properties of incident waves. We have also investigated the influence of extended sources (as a typical feature of type III radio bursts) on measured spectral matrices. We have found an empirical relation between apparent source sizes and spectral matrices decomposed by SVD. Abovementioned techniques have been extensively tested on data obtained by the High Frequency Receiver (HFR, a part of S/Waves). We have performed statistical analysis of a...
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Stereoscopic Observations of Solar Radio Emissions by the S/WavesInstrument onboard the STEREO Spacecraft
Krupař, Vratislav
This PhD thesis is primarily dedicated to a study of type III radio bursts observed by the S/Waves instrument onboard Solar TErrestrial RElations Observatory (STEREO). These emissions are produced by beams of suprathermal electrons escaping the corona along open magnetic field lines during increased solar activity. As fast electrons propagate in the interplanetary (IP) medium, Langmuir waves are generated at the local electron plasma frequency fpe by a bump-on-tail instability and can be afterwards converted by a non-linear process into radio emissions at fpe and/or 2fpe: type III radio bursts. We have developed a goniopolarimetric (GP, also referred to as direction-finding) inversion using the Singular Value Decomposition (SVD) technique for electric measurements on three non-orthogonal antennas. It allows us to retrieve both wave vector directions and polarization properties of incident waves. We have also investigated the influence of extended sources (as a typical feature of type III radio bursts) on measured spectral matrices. We have found an empirical relation between apparent source sizes and spectral matrices decomposed by SVD. Abovementioned techniques have been extensively tested on data obtained by the High Frequency Receiver (HFR, a part of S/Waves). We have performed statistical analysis of a...
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Stereoscopic Observations of Solar Radio Emissions by the S/WavesInstrument onboard the STEREO Spacecraft
Krupař, Vratislav ; Santolík, Ondřej (advisor) ; Krucker, Samuel (referee) ; Wimmer-Schweingruber, Robert F. (referee)
This PhD thesis is primarily dedicated to a study of type III radio bursts observed by the S/Waves instrument onboard Solar TErrestrial RElations Observatory (STEREO). These emissions are produced by beams of suprathermal electrons escaping the corona along open magnetic field lines during increased solar activity. As fast electrons propagate in the interplanetary (IP) medium, Langmuir waves are generated at the local electron plasma frequency fpe by a bump-on-tail instability and can be afterwards converted by a non-linear process into radio emissions at fpe and/or 2fpe: type III radio bursts. We have developed a goniopolarimetric (GP, also referred to as direction-finding) inversion using the Singular Value Decomposition (SVD) technique for electric measurements on three non-orthogonal antennas. It allows us to retrieve both wave vector directions and polarization properties of incident waves. We have also investigated the influence of extended sources (as a typical feature of type III radio bursts) on measured spectral matrices. We have found an empirical relation between apparent source sizes and spectral matrices decomposed by SVD. Abovementioned techniques have been extensively tested on data obtained by the High Frequency Receiver (HFR, a part of S/Waves). We have performed statistical analysis of a...
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Analysis of propagation of "lion roar" emissions using the data of the Cluster spacecraft
Krupař, Vratislav ; Santolík, Ondřej (advisor) ; Souček, Jan (referee)
The main task of this thesis was a statistical study of lion roar wave emissions in the Earth's magnetosheath. Large data set obtained from the Cluster spacecraft has been used. We have studied a frequency distribution, a wave power distribution and a spatial distribution. We have investigated propagation characteristics using advanced methods applied on multi-components measurement. We have confirmed the narrow-band structure of lion roars. We have compared observed and estimated (from the cold plasma theory) time lags between spacecraft during short separations.
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Calibration of the STEREO/WAVES Instrument in the Solar Wind
Krupař, Vratislav ; Maksimovic, M. ; Cecconi, B. ; Santolík, Ondřej
The S/WAVES instrument onboard the STEREO spacecraft measures electromagnetic waves in the solar wind. This unique project allows us to investigate properties of type II and type III radio bursts related with solar flares and propagation of coronal mass ejections (CMEs) in the interplanetary medium, respectively. In this paper we present properties of the High Frequency Receiver (HFR) receiver which covers the frequency range 125 kHz–16.025 MHz. We have compared the gains from the two HFR channels and we have found significant variations of these gains with time. We have proposed a solution for correcting these gain variations and improving the S/WAVES HFR calibrations in order to get as accurate goniopolarimetric measurements as possible.
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