|
| |
|
|
Ray tracing simulations of wave propagation in planetary magnetospheres
Hanzelka, Miroslav ; Santolík, Ondřej (advisor) ; Chum, Jaroslav (referee)
Electromagnetic (EM) waves in plasma influence the dynamics of plane- tary magnetospheres and affect the cosmic environment in orbital regions of man-made satellites. In this thesis, we present space physics applications of the ray tracing method as a tool for studying the propagation of plasma waves in the approximation of geometrical optics. Based on a simulation in cold plasma approximation we explain observed and unexpected changes in the wave vector direction of quasiperiodic waves measured by the low-orbit satellite DEMETER. We also studied, with the use of a hot plasma ray tra- cing code developed as a part of this thesis, the behavior of chorus emissions in the Earth's outer magnetosphere, focusing on the possible ducting of these whistler mode waves and the evolution of wave magnetic energy. We show that large portion of chorus emissions observed by the Cluster spacecraft must be ducted and conclude that while the linear theory cannot fully ex- plain observed wave growth, it can make up a large portion of the observed increase in energy in the low and mid-latitudinal regions. Lastly, we present propagation characteristics of EM proton cyclotron waves in the water-ion rich magnetosphere of Saturn and we show that in contrast to observations in the Earth's magnetosphere, a direct observation of...
|
|
|
Spacecraft observations of waves in low-latitude magnetospheric plasma
Sochorová, Zuzana ; Santolík, Ondřej (advisor) ; Chum, Jaroslav (referee) ; Tichý, Milan (referee)
Title: Spacecraft observations of waves in low-latitude magnetospheric plasma Author: Zuzana Sochorová Department: Department of Surface and Plasma Science Supervisor: prof. Ondřej Santolík, Department of Surface and Plasma Science, Institute of Atmospheric Physics AS CR Abstract: The present doctoral thesis is based on the analysis of the electromagne- tic equatorial noise (EN) emissions. These waves propagate in the vicinity of the geomagnetic equator at frequencies between the local proton cyclotron frequency and the lower hybrid frequency. We used data obtained by the 4 Cluster spacecraft during the period from January 2001 to December 2010. The analysis is based on the data from the STAFF-SA instrument. We have developed 3 selection criteria for the visual identification and we have compiled a database of more than 2000 events. We demonstrate than EN occurs in almost entire analyzed range of the McIlwain's parameter from about L ∼ 1 to L ∼ 10. EN mostly occurs between L = 3 and L = 5.5. Analysis of occurrence rates as a function of magnetic local time shows strong variations outside of the plasmasphere (with an increase in the afternoon sector), while the occurrence rate inside the plasmasphere is almost independent. We have also analyzed the inner structure of EN. We use data from the WBD instrument...
|
|
| |
|
|
Analysis of multidimensional measurements of electromagnetic waves in the Earth's magnetosphere
Pechal, Radim ; Přech, Lubomír (advisor) ; Chum, Jaroslav (referee)
Title: Analysis of multidimensional measurements of electromagnetic waves in the Earth's magnetosphere Author: Radim Pechal Department: Department of Surface and Plasma Science Supervisor: doc. RNDr. Lubomír Přech, Dr. Supervisor's e-mail address: Lubomir.Prech@mff.cuni.cz Abstract: The thesis introduces into basic knowledge of waves in plasma, especially waves in the Earth's magnetosphere. There are mentioned some space projects focused on chorus waves. The second part of this thesis is a laboratory study of ELMAVAN device that is being developed within Resonance project. The main part of the thesis describes methods of onboard processing of measured LF electromagnetic field data and implementation of calculations in Field Programmable Gate Array. An important part of the thesis is a preparation of input data required for testing and verification of the FPGA program. Keywords: waves in plasma, chorus wave, Resonance project, ELMAVAN, FPGA
|
|
|
3D Scene Reconstruction from Stereo Pictures
Turoňová, Beata ; Chum, Jaroslav (referee) ; Holub, Viliam (advisor)
We study 3D scene reconstruction from stereo pictures. First, we describe methods for computing fundamental matrix from a set of corresponding image points. Using this matrix we can obtain a projective 3D reconstruction. The second part deals with techniques of re ning the projective reconstruction to metric one. We focus especially on that one, which uses an essential matrix. Furthermore we discuss the possibilities of surface reconstruction from a given point cloud. The last part includes some details of an implementation and presents its results.
|
|
| |
|
| |
|
|
Seasonal Variation in Propagation Directions of Acoustic Gravity Waves in the Thermosphere
Fišer, Jiří ; Chum, Jaroslav
We investigate seasonal behaviour of acoustic gravity waves (AGWs) in\nthe thermosphere. For this purpose, measurements of HF Doppler sounding stations\noperated by or in cooperation with our institute are used. These measurements\nare compared with previously reported studies which employed different techniques\nof ionospheric observations. The propagation of AGWs is found to have strong\nseasonal dependence. AGWs in summer generally tend to propagate poleward in\nsummer and equatorward in winter.
|
|
|
HF Doppler Observations of Ionospheric Disturbances over Taiwan
Fišer, Jiří ; Chum, Jaroslav
Results of observations of traveling ionospheric disturbances (TIDs) by the multipath continuous HF Doppler sounding system operating in Taiwan are presented. We analysed one-year long period of measurements from April 2014 to March 2015 and investigated horizontal velocities and azimuths of propagation of medium scale traveling ionospheric disturbances (MSTIDs) with periods from 4 min to 60 min. Horizontal velocities range from ≈ 100 m s−1 to ≈ 300 m s−1 and MSTIDs propagate preferentially south-eastward in the local winter and preferentially northward in the local summer. The disturbances rarely propagate with azimuth in the range of 200–290◦ .
|
guest ::
