Ne (105)
Použitá omezení
(4)
Počet nalezených dokumentů:
105
Publikováno od
do
Dependence of the Sweep Rate of Whistler-mode Chorus Emissions on the Plasma Density
Macúšová, Eva; Santolík, Ondřej; Gurnett, D. A.; Pickett, J. S.; Nunn, D.; Trakhtengerts, V. Y.; Demekhov, A. G.; Titova, E. E.; Kozelov, V.; Rycroft, M. J.
2007 - anglický
Whistler-mode chorus consists of intense electromagnetic wave packets generated by a nonlinear mechanism involving wave-particle interactions. Chorus wave packets are discrete frequency-time structures in a frequency range from a few hundreds of Hz to several kHz changing their frequency on a time scale from a few tenths of seconds to a few seconds. The source region of chorus emissions is localised close to the geomagnetic equatorial plane. Our investigation is based on multipoint measurements of the wideband (WBD) plasma wave instruments on board the four Cluster spacecraft. We investigate the sweep rate of the chorus frequency as a Whistler-mode chorus consists of intense electromagnetic wave packets generated by a nonlinear mechanism involving wave-particle interactions. Chorus wave packets are discrete frequency-time structures in a frequency range from a few hundreds of Hz to several kHz changing their frequency on a time scale from a few tenths of seconds to a few seconds. The source region of chorus emissions is localised close to the geomagnetic equatorial plane. Our investigation is based on multipoint measurements of the wideband (WBD) plasma wave instruments on board the four Cluster spacecraft. We investigate the sweep rate of the chorus frequency as a function of the cold plasma density in the equatorial plane and then we compare it A theoretical model, numerical simulations and also our preliminary results from the measurements predict an increasing sweep rate with decreasing cold plasma density.
Klíčová slova:
Chorus Emissions
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Dependence of the Sweep Rate of Whistler-mode Chorus Emissions on the Plasma Density
Whistler-mode chorus consists of intense electromagnetic wave packets generated by a nonlinear mechanism involving wave-particle interactions. Chorus wave packets are discrete frequency-time ...
Preparation of a Database for the Study of Scaling Phenomena in the Ionosphere
Mošna, Zbyšek; Šauli, Petra; Santolík, Ondřej
2007 - anglický
The correct forecast of the state of the ionosphere requires understanding of all the effects which influence its behaviour as well as the extent of the relationships in the system. A convenient way how to analyse large data sets and describe the coupling or disconnection at various time scales is to study the scaling phenomena. For the computations of scaling properties of the processes that influence the ionosphere dynamics we have prepared a database of several characteristics that describe the coupling processes in the solar-magnetosphere-ionosphere system. This data are of sufficient length and sampling density to verify the presence or absence of links between the processes under study. Popis dostupných dat a nástin jejich plánovaného zpracování.
Klíčová slova:
scaling phenomena; solar-magnetosphere-ionosphere coupling
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Preparation of a Database for the Study of Scaling Phenomena in the Ionosphere
The correct forecast of the state of the ionosphere requires understanding of all the effects which influence its behaviour as well as the extent of the relationships in the system. A convenient way ...
Ionospheric F-region Drift Measurements, First Results for Winter 2006
Kouba, Daniel; Šauli, Petra; Boška, Josef; Santolík, Ondřej
2006 - anglický
We describe step by step a newly improved method of drift velocity evaluation: (i) height range selection, (ii) Doppler frequency shift value limitation, and (iii) choice of the maximum incidence angle. Our preliminary results describe drift velocity behaviour during quiet geomagnetic conditions for the winter season for station Pruhonice. Krok po kroku popisujeme nově vyvinutou matodu pro výpočet rychlostí ionosférických driftů (i, určení správného výškového rozsahu; ii, omezení uvažovaných hodnot Dopplerova posunu; iii, volba maximálního úhlu dopadu). Naše předběžné výsledky popisují chování driftových rychlostí za klidných geomagnetických podmínek v zimním období na stanici Průhonice.
Klíčová slova:
Ionospheric drift; Skymap; Digisonde
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ionospheric F-region Drift Measurements, First Results for Winter 2006
We describe step by step a newly improved method of drift velocity evaluation: (i) height range selection, (ii) Doppler frequency shift value limitation, and (iii) choice of the maximum incidence ...
Modelling of the wind speed profiles obtained by a sodar in complex terrain
Hošek, Jiří
2005 - anglický
The wind profiles with two Doppler sodars were measured in wide range of synoptic situations in Ore mountains (Erzgebirge) and in the region of Orlické hory (mountains), both in the Czech republic. Ore mountains represent the region most suitable for construction of wind turbines in the Czech republic. Concerning the observed wind profiles, their generalization may serve for improvement of precision of the simulated wind profile fields. In the second part of the work, we performed the modelling of wind speed profiles in the complex terrain of above-mentioned mountain ranges. We have applied the non-hydrostatic meso-scale models KAMM and PIAP. The numerical simulations with the models were performed for different situations of the ambient flow, described by geostrophic wind speed and direction, and temperature stratification. Sodarová měření byla prováděna na vhodných lokalitách Krušných a Orlických hor v letech 2000 a 2003 v široké škále synoptických situací. Krušné hory představují nejvhodnější oblast ke stavbě větrných elektráren. Zobecnění získaných profilů rychlosti větru může pomoci zlepšit přesnost numerických modelů v takových výškách nad povrchem, které jsou významné pro stavbu větrných elektráren. Ve druhé části práce jsou v obou oblastech počítána pole rychlosti větru pro termíny získaných vertikálních profilů. Použity byly nehydrostatické mezoměřítkové modely KAMM a PIAP. Inicializace modelů byla provedena rychlostí a směrem geostrofického proudění a teplotním zvrstvením.
Klíčová slova:
wind profile; sodar; boundary layer; complex terrain
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling of the wind speed profiles obtained by a sodar in complex terrain
The wind profiles with two Doppler sodars were measured in wide range of synoptic situations in Ore mountains (Erzgebirge) and in the region of Orlické hory (mountains), both in the Czech republic. ...
On methods distinguishing drop size distribution type for improved estimation of radiowave attenuation due to rain
Fišer, Ondřej
2003 - anglický
The contribution shows some criteria to distinguish the rain types (related to the drop size distribution-DSD types) aimed at improved rain attenuation estimation.
Klíčová slova:
drop size distribution; rain types; radar reflectivity factor
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
On methods distinguishing drop size distribution type for improved estimation of radiowave attenuation due to rain
The contribution shows some criteria to distinguish the rain types (related to the drop size distribution-DSD types) aimed at improved rain attenuation estimation.
Sources of the cusp plasma for the different sign of IMF By
Šimůnek, Jiří; Šafránková, J.; Němeček, Z.; Wing, S.
2002 - anglický
The importance of the interplanetary magnetic field (IMF) direction for the cusp formation was dicovered a long time ago. A sign of the IMF Bz component is believed to be responsible for a location of the plasma entry into the cusp. The paper uses the INTERBALL-1 and MAGION-4 data to study the high-altitude cusp topology for different IMF By orientations. The study reveals the importance of IMF horizontal components on the cusp configuration as well as on small-scale processes at the outer cusp. We discuss an influence of the tilt angle of the Earth's dipole on these processes.
Klíčová slova:
cusp plasma; magnetopause; INTERBALL-1
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Sources of the cusp plasma for the different sign of IMF By
The importance of the interplanetary magnetic field (IMF) direction for the cusp formation was dicovered a long time ago. A sign of the IMF Bz component is believed to be responsible for a location of ...
LHR associated oblique noise bands
Chum, Jaroslav; Jiříček, František; Shklyar, D.
2002 - anglický
Observations onboard the Magion-5 satellite revealed oblique noise bands above the local Lower Hybrid Resonance (LHR) frequency - wave phenomena, which (to the best of authors' knowledge) have not been discussed yet. Examples of such oblique bands, both in review (large time-scale) spectrograms, and in detailed (small time-scale) spectrograms are presented. Based on ray-tracing simulations, an explanation of these oblique bands is suggested.
Klíčová slova:
lower hybrid resonance; MAGION-5; plasmapause
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
LHR associated oblique noise bands
Observations onboard the Magion-5 satellite revealed oblique noise bands above the local Lower Hybrid Resonance (LHR) frequency - wave phenomena, which (to the best of authors' knowledge) have not ...
PERUN - the System for the Crop Yield Forecasting
Dubrovský, Martin; Žalud, Z.; Trnka, M.; Pešice, Petr; Haberle, J.
2002 - anglický
PERUN 1.0 is the Windows-based system for probabilistic crop yield forecasting. It is based on crop growth model WOFOST. The weather series is prepared by a stochastic weather generator Met&Roll with parameters that are derived from the observed series.
Klíčová slova:
forecasting; crop model; weather generator
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
PERUN - the System for the Crop Yield Forecasting
PERUN 1.0 is the Windows-based system for probabilistic crop yield forecasting. It is based on crop growth model WOFOST. The weather series is prepared by a stochastic weather generator Met&Roll with ...
Meteorological elements in the growth and development of selected cereal crop - applicability of regression analysis method
Trnka, M.; Žalud, Z.; Semerádová, Daniela; Dubrovský, Martin
2002 - anglický
Relationships between meteorological elements and the growth and development characteristics of selected cereal crop is assessed.
Klíčová slova:
regression analysis; spring barley
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Meteorological elements in the growth and development of selected cereal crop - applicability of regression analysis method
Relationships between meteorological elements and the growth and development characteristics of selected cereal crop is assessed.
Performance and Reliability of Advanced Telecommunication Systems Using Millimetre Wavelengths in the Czech Republic
Kvičera, V.; Fišer, Ondřej; Mazánek, M.
2001 - anglický
This contribution informs about the launched GACR grant, its aims and methods. The aim is to improve the radio link planning with respect to the influence of the atmosphere. Particular topics are: radio refractive study and measurements, long term rain rate statistics and its stability, experimental measurement of attenuation on 58 GHz link and comparison of predicted and measured atmospheric attenuation.
Klíčová slova:
radio wave propagation; atmospheric attenaation; refractive index
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Performance and Reliability of Advanced Telecommunication Systems Using Millimetre Wavelengths in the Czech Republic
This contribution informs about the launched GACR grant, its aims and methods. The aim is to improve the radio link planning with respect to the influence of the atmosphere. Particular topics are: ...
NUŠL poskytuje centrální přístup k informacím o šedé literatuře vznikající v ČR v oblastech vědy, výzkumu a vzdělávání. Více informací o šedé literatuře a NUŠL najdete na webu služby.
Vaše náměty a připomínky posílejte na email nusl@techlib.cz
Provozovatel
Zahraniční báze