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Impact of ionosphere changes on GNSS signals reception
Navrátilová, Karolína ; Šplíchal, Miroslav (referee) ; Vosecký, Slavomír (advisor)
This thesis examines the impact of the ionosphere on the propagation of signals from Global Navigation Satellite Systems (GNSS). The ionosphere, characterized as an ionized layer of Earth's atmosphere, affects the propagation of electromagnetic waves in a way that can significantly degrade the accuracy of GNSS signals. The work describes the basic characteristics of the ionosphere, including its layers and the effects of solar and geomagnetic activity. In the practical part, data from measurements conducted on various days are analyzed, comparing the behavior of single-frequency and dual (GPS and GLONASS) receivers depending on ionospheric conditions.
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Signal Filtration for Detecting Electromagetic Emission
Podshivalov, Aleksandr
There are many methods to describe and study geological processes. This paper deals with a data measured by a loop antenna in a dripstone cave. The measuring system, the sequence of the experiment, and result of signal filtering and spectral analysis were described. Several artificial noise sources in different frequency of signal spectrum bands were found. Signal filtering was carried out. On the basis of the filtered signal central moments during a few days were calculated.
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Antenna design for ULF- Low-level magnetic measurements
Škoda, Martin ; Kříž, Tomáš (referee) ; Fiala, Pavel (advisor)
The present work deals with the design and study of the sensing element (antenna) for ultra low level measurements of low frequency magnetic fields. At the first, it considers the propagation of electromagnetic fields and form of propagation of electromagnetic waves. Then, using Ansys Maxwell are simulated by three models sensing elements. At the end of thesis, two antennas are implemented and conducted laboratory measurements with them.
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Total Electron Content Measurements by Single-Frequency GPS Receiver
Rejfek, Luboš ; Pitaš, K. ; Urbář, Jaroslav ; Chmelař, P.
In this paper is described the measurement of the Total Electron Content by the single-frequency GPS receiver. Disadvantage of this method is that it cannot be used for realtime processing. The advantages of the proposed method are that the device is cheaper than dual-frequency GPS receiver and it can reinterpret older valuable measurements by such singlefrequency receivers. The algorithm was tested with the dualfrequency receiver. Signal from selected frequency (f1, or f2) was processed by presented algorithm and results were compared with standard processing of the signals, which is used for the dual-frequency receivers. Results are promising.
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Digisonde measurement
Kouba, Daniel ; Mošna, Zbyšek ; Koucká Knížová, Petra ; Boška, Josef ; Rejfek, Luboš
Ionospheric station in Průhonice currently performs its measurements using Digisonda DPS 4D. The vertical profile of the electron concentration can be measured by ionospheric vertical sounding using Ionosonde and Digisonde. The electron concentration profile shows the location of the layers of the ionosphere, the D, E, F1 and F2 layers, and the electron concentration at a given height. Another way to study the behavior of the ionosphere is to measure Doppler shift in ionospheric plasma. The Průhonická observatory is part of the Digisond World Network. The measured data is immediately automatically sent to the GIRO database (http://ulcar.uml.edu/DIDBase/).
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Signal Filtration for Detecting Electromagetic Emission
Podshivalov, Aleksandr
There are many methods to describe and study geological processes. This paper deals with a data measured by a loop antenna in a dripstone cave. The measuring system, the sequence of the experiment, and result of signal filtering and spectral analysis were described. Several artificial noise sources in different frequency of signal spectrum bands were found. Signal filtering was carried out. On the basis of the filtered signal central moments during a few days were calculated.
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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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Impact of the troposphere on the inosphere
Koucká Knížová, Petra ; Mošna, Zbyšek ; Potužníková, Kateřina ; Boška, Josef ; Kouba, Daniel
Ionosphere represents weakly ionized plasma that reflects solar and geomagnetic activity and processes\nin the neutral atmosphere. Correlation of long time series of the ionospheric plasma critical frequencies,\nobtained by mean of vertical sounding from European stations, is analysed with respect to latitudinal and\nlongitudinal difference and surface distance of stations. Time series of critical frequencies are highly correlated\nreflecting the dominant solar influence. Correlation coefficients are high not only for raw data and subtracted\nmean courses but for fluctuations around mean as well. At the surface distance exceeding 1000 km and/ or about\n10 degrees of latitudinal difference between stations, the correlation coefficients of fluctuations decrease\nrapidly. Such effect is less visible on the latitudinal dependence, where the correlation coefficients decrease with\nincreasing distance with less pronounced threshold. We explain the existence of the ‘break point’ at 10 degrees\nin longitude and/or 1000 km by the ‘local’ influence of the neutral atmosphere and the wave activity. As a\npossible source of the common influence on scale 1000 km/10 degree we propose tropospheric systems that are\nknown to be an important source of atmospheric waves in a broad period range. Large tropospheric mesoscale\nsystems have typically up to 2000 km in size.
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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.
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Antenna design for ULF- Low-level magnetic measurements
Škoda, Martin ; Kříž, Tomáš (referee) ; Fiala, Pavel (advisor)
The present work deals with the design and study of the sensing element (antenna) for ultra low level measurements of low frequency magnetic fields. At the first, it considers the propagation of electromagnetic fields and form of propagation of electromagnetic waves. Then, using Ansys Maxwell are simulated by three models sensing elements. At the end of thesis, two antennas are implemented and conducted laboratory measurements with them.
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