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Solar Wind Modification in the Earth Foreshock
Urbář, Jaroslav ; Němeček, Zdeněk (advisor) ; Souček, Jan (referee) ; Vandas, Marek (referee)
Title: Solar Wind Modification in the Earth Foreshock Author: Jaroslav Urbář Department: Department of Surface and Plasma Science Supervisor: Prof. Zdeněk Němeček, Department of Surface and Plasma Science Abstract: The thesis presents statistical studies of the solar wind deceleration and deflection in the foreshock and its potential causes. The multi-point observa- tions from the THEMIS mission in the foreshock are compared with a Wind solar wind monitor with motivation to estimate different factors influencing evolution of solar wind speed and its deflection. We have found a systematic deceleration of the solar wind mainly due to its proton component with a decreasing distance to the bow shock that is controlled by the compressibility and the level of magnetic field fluctuations in the ULF wave range associated with the flux of reflected and accelerated particles. We can conclude that the reflected particles excite waves of large amplitudes that decelerate the solar wind protons throughout the foreshock as well as in front of the Moon. Keywords: Earth foreshock; reflected protons; solar wind proton velocity recon- struction; deceleration; ULF waves 1
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Dynamics of the bow shock and magnetopause
Jelínek, Karel ; Němeček, Zdeněk (advisor) ; Kudela, Karel (referee) ; Vandas, Marek (referee)
viii Title: Dynamics of the bow shock and magnetopause Author: Karel Jelínek Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Zdeněk Němeček, DrSc. Department of Surface and Plasma Science e-mail address: zdenek.nemecek@mff.cuni.cz Abstract: The interplanetary space is a unique laboratory which allows us to dis- cover (i) a behavior of the plasma under different conditions, (ii) origin of its insta- bilities, and (iii) its interaction with obstacles such as the Earth's magnetosphere. The present thesis analyzes the outer Earth's magnetosphere. The results are based on the in situ sensing by a variety of the spacecraft (e.g., IMP-8, INTERBALL-1, MAGION-4, Geotail, Cluster-II and Themis). The solar wind curently monitored by the WIND and ACE spacecraft near the La- grange point L1 affects by its dynamic pressure the Earth's magnetic field which acts as a counter-pressure and the boundary where these pressures are balanced is the magnetopause. Due to supersonic solar wind speed, the bow shock forms in front of the magnetopause and a region in between, where plasma flows around an obstacle is named the magnetosheath. The thesis contributes to a deaper understanding of the dependence of magnetopause and bow shock shapes and positions, especially, (1) on the orientation of the inter-...
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Airport - Time and resource constrained project sheduling
Vandas, Marek ; Petříčková, Zuzana (advisor) ; Pangrác, Ondřej (referee)
This thesis identifies constraints for safe ground airport operations. These operations consist of runway assignment, taxi operations planning and gate scheduling. The aim of this thesis is to show how this problem can be formulated as constraint satisfaction problem and then solved as a scheduling problem. Based on this model, an application that ilustrates these concepts is designed and implemented. This application enables a visualisation of results. An extendable constraint solver was implemented for the purpose of this application. This solver can be used to solve problems from other domains as well and also enables easy change of search strategy.
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Correlation properties of magnetosheath fluctuations
Gutynska, Olga ; Šafránková, Jana (advisor) ; Vandas, Marek (referee) ; Souček, Jan (referee)
Title: Correlation properties of magnetosheath fluctuations Author: Olga Gutynska Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc. e-mail address: Jana.Safrankova@mff.cuni.cz Abstract: This thesis deals with fluctuations of the magnetic field (MF) and plasma density in different magnetosheath locations. The statistical study of the correlation length of these quantities has shown that these lengths are surprisingly low for both the ion flux and MF (approx. 1 RE). However, the correlation length increases with an increasing correlation between the magnetosheath and interplanetary magnetic fields (IMF). Further, we have found that the correlation length of MF fluctuations depends on the solar wind speed, on a correlation between IMF and magnetosheath MF fluctua- tions, and on the amplitude of fluctuations. The statistical study of radial profiles of cross-correlations between MF and plasma density at the subsolar and flank regions based on Cluster and THEMIS magnetosheath observa- tions revealed better correlations toward the magnetopause. A study of the modification of the IMF direction in the magnetosheath has shown that a reliable prediction of the magnetosheath BZ sign requires |IMF BZ| > 2 nT and that this prediction is more precise during solar minimum....
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Solar Wind Modification in the Earth Foreshock
Urbář, Jaroslav ; Němeček, Zdeněk (advisor) ; Souček, Jan (referee) ; Vandas, Marek (referee)
Title: Solar Wind Modification in the Earth Foreshock Author: Jaroslav Urbář Department: Department of Surface and Plasma Science Supervisor: Prof. Zdeněk Němeček, Department of Surface and Plasma Science Abstract: The thesis presents statistical studies of the solar wind deceleration and deflection in the foreshock and its potential causes. The multi-point observa- tions from the THEMIS mission in the foreshock are compared with a Wind solar wind monitor with motivation to estimate different factors influencing evolution of solar wind speed and its deflection. We have found a systematic deceleration of the solar wind mainly due to its proton component with a decreasing distance to the bow shock that is controlled by the compressibility and the level of magnetic field fluctuations in the ULF wave range associated with the flux of reflected and accelerated particles. We can conclude that the reflected particles excite waves of large amplitudes that decelerate the solar wind protons throughout the foreshock as well as in front of the Moon. Keywords: Earth foreshock; reflected protons; solar wind proton velocity recon- struction; deceleration; ULF waves 1
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Fast solar wind helium abundance variations and their relations to solar processes
Ďurovcová, Tereza ; Šafránková, Jana (advisor) ; Vandas, Marek (referee)
Helium can significantly influence solar wind dynamics. The changes of its relative abundance are usually associated with crossings of the boundaries between adjacent flux tubes. However, the recent studies of the data from the BMSW instrument onboard the Spektr-R spacecraft show that the relative helium abundance could vary also inside the flux tubes. The differential motion of proton and helium solar wind components was suggested as a source of turbulence inside the flux tube. The thesis is devoted to the long-term statistical study of the fast helium abundance variations with respect to parameters of the solar wind and changes of its source region. For this purpose, the plasma data from the instruments onboard the Wind and the Spektr-R spacecraft and magnetic field measurements from Wind were used. Simultaneous changes of the relative helium abundance and solar wind parameters were investigated in the long-term Wind observations as well as in the observations prior to and behind interplanetary shocks. Finally, the study of differences between proton and helium velocities during solar minima and solar maxima was conducted.
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MHD discontinuities in the solar wind and their relation to processes in the Earth magnetosphere
Goncharov, Oleksandr ; Šafránková, Jana (advisor) ; Souček, Jan (referee) ; Vandas, Marek (referee)
1 Title: MHD discontinuities in the solar wind and their relation to processes in the Earth magnetosphere Author: Oleksandr Goncharov Department / Institute: Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University Supervisor of the doctoral thesis: Prof. RNDr. Jana Safrankova, DrSc Abstract: Collisionless shocks are ubiquitous in the heliosphere from the outer corona to the termination shock. They play an important role in the interaction of the solar wind with the planets because they efficiently convert the energy of the directed ion flow into the energy of heated ions and electrons, the energy of the enhanced magnetic field, and the energy of the accelerated particles. The leading idea of the thesis is to investigate evolution of distinct solar wind features, predominantly interplanetary shocks, within the solar wind, their interaction with the outer magnetospheric boundaries (magnetopause and bow shock), and to follow a path of resulting discontinuities through the magnetosphere up to its far tail. The methodology is based on the statistical evaluation of multispacecraft observations as well as on case studies of particular events. Some experimental investigations are supported with computer modeling. Moreover, an application of fast plasma measurements of the...
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Relationship of helium abundance in the solar wind to solar activity
Cagaš, Petr ; Šafránková, Jana (advisor) ; Vandas, Marek (referee)
Rapid changes in relative helium abundance in solar wind are often attributed to the flux tube crossings - thus between solar wind streams coming from different parts of the solar corona. Recent studies however show, that the changes in relative helium abundance are not always correlated with changes in other parameters and therefore the relative helium abundance could be changed even during the propagation of solar wind inside a flux tube. The topic of this thesis is an analysis of rapid changes of solar wind parameters and their mutual connection. Using a multipoint (we use data from the SPEKTR-R, WIND and the THEMIS spacecraft) case study of interplanetary shocks, we show that a possible explanation of those changes could be a magnetosonic instability excited by the differential flow between helium and proton populations.
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Correlation properties of magnetosheath fluctuations
Gutynska, Olga ; Šafránková, Jana (advisor) ; Vandas, Marek (referee) ; Souček, Jan (referee)
Title: Correlation properties of magnetosheath fluctuations Author: Olga Gutynska Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc. e-mail address: Jana.Safrankova@mff.cuni.cz Abstract: This thesis deals with fluctuations of the magnetic field (MF) and plasma density in different magnetosheath locations. The statistical study of the correlation length of these quantities has shown that these lengths are surprisingly low for both the ion flux and MF (approx. 1 RE). However, the correlation length increases with an increasing correlation between the magnetosheath and interplanetary magnetic fields (IMF). Further, we have found that the correlation length of MF fluctuations depends on the solar wind speed, on a correlation between IMF and magnetosheath MF fluctua- tions, and on the amplitude of fluctuations. The statistical study of radial profiles of cross-correlations between MF and plasma density at the subsolar and flank regions based on Cluster and THEMIS magnetosheath observa- tions revealed better correlations toward the magnetopause. A study of the modification of the IMF direction in the magnetosheath has shown that a reliable prediction of the magnetosheath BZ sign requires |IMF BZ| > 2 nT and that this prediction is more precise during solar minimum....
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