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Magnetic reconnection in the solar wind
Enžl, Jakub ; Přech, Lubomír (advisor)
Magnetic reconnection is a fundamental process that changes magnetic field configuration and converts a magnetic energy to flow energy and plasma heating. It can be found in a plasma with frozen magnetic field lines at boundaries where different magnetic field topologies encounter each other and thin current sheets are created as it is typical in the solar wind. In the thesis, we have used spacecraft measurements of solar wind plasma and magnetic field to found magnetic reconnection exhausts. We analyze and compare them with theoretical predictions. The results of the statistical analysis oriented on re-distribution of the magnetic energy in reconnection showed that both a portion of the energy deposited into heat as well as the energy spent on an acceleration of the exhaust plasma increase with the magnetic shear angle in accord with the increase of the magnetic flux available for reconnection. Moreover, we identify unusual events in the solar wind; we found magnetic reconnection exhausts accompanied by one or two side jets and explained their possible causes.
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Magnetic reconnection in the solar wind
Enžl, Jakub ; Přech, Lubomír (advisor) ; Bárta, Miroslav (referee) ; Kulhánek, Petr (referee)
Magnetic reconnection is a fundamental process that changes magnetic field configuration and converts a magnetic energy to flow energy and plasma heating. It can be found in a plasma with frozen magnetic field lines at boundaries where different magnetic field topologies encounter each other and thin current sheets are created as it is typical in the solar wind. In the thesis, we have used spacecraft measurements of solar wind plasma and magnetic field to found magnetic reconnection exhausts. We analyze and compare them with theoretical predictions. The results of the statistical analysis oriented on re-distribution of the magnetic energy in reconnection showed that both a portion of the energy deposited into heat as well as the energy spent on an acceleration of the exhaust plasma increase with the magnetic shear angle in accord with the increase of the magnetic flux available for reconnection. Moreover, we identify unusual events in the solar wind; we found magnetic reconnection exhausts accompanied by one or two side jets and explained their possible causes.
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Structure, Location, and Dynamics of the Magnetopause
Grygorov, Kostiantyn ; Přech, Lubomír (advisor) ; Bárta, Miroslav (referee) ; Hayosh, Mykhaylo (referee)
Title: Structure, Location, and Dynamics of the Magnetopause Author: Kostiantyn Grygorov Department: Department of Surface and Plasma Science Supervisor: Doc. RNDr. Lubomír Přech, Dr., Department of Surface and Plasma Science e-mail address: Prech@mbox.troja.mff.cuni.cz Abstract: The magnetopause is the key region where the collisionless plasma from the Sun penetrates into the Earth's magnetosphere. A transfer of the plasma, momentum, and energy across the magnetopause is highly variable and depends on solar wind conditions, similarly as the magnetopause location. This thesis addresses the solar wind-magnetosphere interaction in two different regions: the dayside equatorial magnetopause and the far magnetotail. In the first part of the thesis, we present a detailed analysis of the interplanetary (IP) shock propa- gation through the solar wind, its impact on the substorm development and its influence on the far magnetotail. We demonstrate that the change of the solar wind VZ component across the shock creates a huge kink that propagates along the tail. The second part of the thesis is devoted to the influence of prolonged intervals of a radial interplanetary magnetic field (IMF) on the dayside magnetopause. The statistical analysis of the equatorial magnetopause shape and location based on THEMIS observations...
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Study of ionospheric F2 layer dynamics using Digisonde DPS-4 measurements in Pruhonice observatory
Kouba, Daniel ; Koucká Knížová, Petra (advisor) ; Ondrášková, Adriena (referee) ; Přech, Lubomír (referee)
Title: Ionospheric drift measurements Author: Daniel Kouba Department: Department of Surface and Plasma Science Supervisor: RNDr. Petra Koucká Knížová, Ph.D. Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic Abstract: This thesis deals with ionospheric drift measurements using Digisonde DPS-4. The results are divided into theoretical and practical part. It is shown that for drift data processing it is necessary to choose correct reflection points corresponding to drift movements first. The selection is made in three steps: restriction of Doppler frequency shift, height range selection, choice of the maximum zenith angle. After- wards it is possible to credibly estimate the vector of drift velocity. The experimental results of drift measurements are based on data from the Pru- honice station. To study the common behavior of ionospheric drifts during quiet conditions, the statistical characteristics of drift velocity components are investiga- ted in layers E and F during geomagnetic quiet year 2006. The maximal daily amplitude of horizontal velocity demonstrates the influence of geomagnetic activity. It is proved to be considerable in the F layer meanwhile it was not observed in the E layer. The effect of strong geomagnetic disturbances is shown at two examples of extreme storms. The...
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Evolution of interplanetary coronal mass ejections
Lynnyk, Andrii ; Vandas, Marek (advisor) ; Přech, Lubomír (referee) ; Rušín, Vojtěch (referee)
Title: Evolution of Interplanetary Coronal Mass Ejections Author: Andrii Lynnyk Department: Department of Surface and Plasma Science Supervisor: RNDr. Marek Vandas, DrSc. e-mail address: vandas@ig.cas.cz Abstract: This thesis deals with deformation of the Interplanetary Coronal Mass Ejections (ICMEs) and their sub-class Magnetic Clouds (MCs) during their propagation in the Solar Wind (SW). The statistical study of the expanded MCs has shown that expansion greatly affects the MC internal magnetic field. We had shown that this influence is more clear for the MCs observed close to their axes. The study of the stand-off shock distance in front of the supersonic ICME confirms a smooth deformation of the ICMEs along their path from the Sun into interplanetary space. We observed that this deformation is increasing with the velocity of the ICME. This study also confirmed the difference in sheaths that are created in front of expanding and non-expanding ICMEs. We found that velocity distribution inside the MC is not uniform and it has large fluctuations. We found that the MC cross-section is usually strongly deformed. Keywords: interplanetary coronal mass ejection, magnetic cloud, magnetosheath, flux rope, magnetic field, shock, fitting
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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
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Functional simulator of the energetic electron detector from the TARANIS project
Enžl, Jakub ; Přech, Lubomír (advisor) ; Němeček, Zdeněk (referee)
Over a signi cant period of time there have been observations of storm-connected phenomena - so called Transient Luminous Events (TLE). In order to perform new measurements, a microsatellite is being developed under a project called TARANIS. The microsatellite is to carry a device designed to measure high-energy electrons IDEE. Its analyser developed at the Department of Surface and Plasma Science (Faculty of Mathematics and Physics, Charles University) should perform overall control of the detector and processing of registered data. The analyzer will also generate an Alert signal to inform other TARANIS devices whenever TLE-related event such as Relativistic Runaway Electon burst is observed. In order to test the analyzer an 4IDEE detector simulator is being developed. It's task is to generate data and send it to the analyzer. The data should be consistent with the ones expected to be measured during TLE. Another phenomenon to be studied by TARANIS is lightning-induced electron precipitation. Registration of such data will be simulated as well.
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