Liquid electrolytes with lower flammability

Bakalářská práce na téma Kapalné elektrolyty se sníženou hořlavostí pojednává o výběru vhodného složení elektrolytu s ohledem na zvýšenou bezpečnost pro použití v lithium-iontových akumulátorech. Hlavním cílem této práce je nalézt toto vhodné složení a dále nalézt vzájemné vztahy mezi měřenými veličinami.The Bachelor’s thesis on subject Liquid electrolytes with lower flammability discusses about selection appropriate composition of electrolyte with consideration of higher safety for use in lithium-ion rechargeable batteries. The main objective of this work is to find that appropriate composition and find mutual relations between measurements.

Parametric analysis of pitch angle scattering and losses of relativistic electrons by oblique EMIC waves

This study analyzes the effects of electromagnetic ion cyclotron (EMIC) waves on relativistic electron scattering and losses in the Earth’s outer radiation belt. EMIC emissions are commonly observed in the inner magnetosphere and are known to reach high amplitudes, causing significant pitch angle changes in primarily >1 MeV electrons via cyclotron resonance interactions. We run test-particle simulations of electrons streaming through helium band waves with different amplitudes and wave normal angles and assess the sensitivity of advective and diffusive scattering behaviors to these two parameters, including the possibility of very oblique propagation. The numerical analysis confirms the importance of harmonic resonances for oblique waves, and the very oblique waves are observed to efficiently scatter both co-streaming and counter-streaming electrons. However, strong finite Larmor radius effects limit the scattering efficiency at high pitch angles. Recently discussed force-bunching effects and associated strong positive advection at low pitch angles are, surprisingly, shown to cause no decrease in the phase space density of precipitating electrons, and it is demonstrated that the transport of electrons into the loss cone balances out the scattering out of the loss cone. In the case of high-amplitude obliquely propagating waves, weak but non-negligible losses are detected well below the minimum resonance energy, and we identify them as the result of non-linear fractional resonances. Simulations and theoretical analysis suggest that these resonances might contribute to subrelativistic electron precipitation but are likely to be overshadowed by non-resonant effects

Deep learning model of hiss waves in the plasmasphere and plumes and their effects on radiation belt electrons

Hiss waves play an important role in removing energetic electrons from Earth’s radiation belts by precipitating them into the upper atmosphere. Compared to plasmaspheric hiss that has been studied extensively, the evolution and effects of plume hiss are less understood due to the challenge of obtaining their global observations at high cadence. In this study, we use a neural network approach to model the global evolution of both the total electron density and the hiss wave amplitudes in the plasmasphere and plume. After describing the model development, we apply the model to a storm event that occurred on 14 May 2019 and find that the hiss wave amplitude first increased at dawn and then shifted towards dusk, where it was further excited within a narrow region of high density, namely, a plasmaspheric plume. During the recovery phase of the storm, the plume rotated and wrapped around Earth, while the hiss wave amplitude decayed quickly over the nightside. Moreover, we simulated the overall energetic electron evolution during this storm event, and the simulated flux decay rate agrees well with the observations. By separating the modeled plasmaspheric and plume hiss waves, we quantified the effect of plume hiss on energetic electron dynamics. Our simulation demonstrates that, under relatively quiet geomagnetic conditions, the region with plume hiss can vary from L = 4 to 6 and can account for up to an 80% decrease in electron fluxes at hundreds of keV at L > 4 over 3 days. This study highlights the importance of including the dynamic hiss distribution in future simulations of radiation belt electron dynamics

Source of the low-altitude hiss in the ionosphere

We analyze the propagation properties of low-altitude hiss emission in the ionosphere observed by DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions). There exist two types of low-altitude hiss: type I emission at high latitude is characterized by vertically downward propagation and broadband spectra, while type II emission at low latitude is featured with equatorward propagation and a narrower frequency band above ∼fcH+. Our ray tracing simulation demonstrates that both types of the low-altitude hiss at different latitude are connected and they originate from plasmaspheric hiss and in part chorus emission. Type I emission represents magnetospheric whistler emission that accesses the ionosphere. Equatorward propagation associated with type II emission is a consequence of wave trapping mechanisms in the ionosphere. Two different wave trapping mechanisms are identified to explain the equatorial propagation of Type II emission; one is associated with the proximity of wave frequency and local proton cyclotron frequency, while the other occurs near the ionospheric density peak

Nonlinear processes in space plasmas and their effects on the generation and propagation of electromagnetic waves

Nonlinear interactions of charged particles and large-amplitude waves have a signif- icant impact on magnetospheric dynamics. Here we focus on the cyclotron resonant interaction between energetic electrons and the discrete, whistler-mode chorus emissions in the Earth's outer radiation belt. The subject is introduced by an extensive review of whistler-mode dispersion properties, resonant electron trajectories and nonlinear wave- growth theories. We then present a new semi-empirical model of rising-tone chorus emis- sions with a fine subpacket structure. The model is then used in test-particle simulations to investigate nonlinear perturbations in hot electron distributions. Based on changes in electron fluxes, we estimate the resolution of spacecraft particle detectors required to detect the predicted perturbations. The test-particle method is further used to sim- ulate atmospheric precipitation of electrons caused by interaction with a single chorus wavepacket, and the result is put into connection with microbursts and pulsating auro- ras. We also detected a violation of the strong diffusion limit by the cyclotron resonant interaction, resulting in loss cone overfilling.

Simulations of spacecraft measurements of electromagnetic waves in the Earth's magnetosphere

For more than fifty years simulations of electromagnetic (EM) wave propa- gation are used to study the Earth's magnetosphere and to analyze EM emissions observed by spacecraft. In this work we focus on the propagation of EM waves in the frequency range from 100 Hz to 10 000 Hz within the region of the inner magnetosphere. We use a numerical procedure which performs ray tracing simu- lations and finds the wave trajectory along with other wave properties. Using these simulations we study propagation properties of equatorial noise emissions. Another subject of this work is development of a propagation scheme explaining a conjugate observation of quasiperiodic emissions by the Van Allen Probe A (VAP-A) spacecraft and the ground station in Athabasca. In this case we make use of a density distribution model based on measurements of plasmaspheric electron density done by the EMFISIS instrument onboard VAP-A.

Ray tracing simulations of wave propagation in planetary magnetospheres

Elektromagnetické (EM) vlny v plazmatu se podílejí na dynamice mag- netosféry Země a dalších planet Sluneční soustavy a významně tak ovlivňují kosmické prostředí v oblastech, kterými procházejí orbity umělých družic. V této práci na několika příkladech ukazujeme možnosti využití metody zva- né ray tracing, která nám umožňuje studovat šíření vln v plazmatu na zákla- dě paprskové aproximace geometrické optiky. Pomocí numerických simulací v přiblížení studeného plazmatu vysvětlujeme prudké změny v orientaci vl- nového vektoru kvaziperiodických emisí pozorovaných nízkoorbitální družicí DEMETER. S využitím programu pro výpočet trajektorií paprsků v disperz- ním prostředí horkého plazmatu, který jsme pro tuto práci vyvinuli, bylo dále studováno šíření EM emisí typu chorus v oblasti vnější magnetosféry Země se zaměřením na vývoj energie vlny podél magnetických siločar a vyhodnocení rozdílů mezi vedeným a nevedeným šířením. Ukazujeme, že chorus pozoro- vaný družicemi Cluster musí být převážně vedený a že ačkoli růst energie nelze zcela vysvětlit pomocí zde aplikované lineární teorie, mají i lineární efekty na růstech nezanedbatelný podíl. Nakonec prezentujeme propagační charakteristiky EM protonových cyklotronových vln v magnetosféře Saturnu bohaté na vodní ionty a ukazujeme, že na rozdíl od zemské magnetosféry je...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...Katedra fyziky povrchů a plazmatuDepartment of Surface and Plasma ScienceMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Simulations of spacecraft measurements of electromagnetic waves in the Earth's magnetosphere

For more than fifty years simulations of electromagnetic (EM) wave propa- gation are used to study the Earth's magnetosphere and to analyze EM emissions observed by spacecraft. In this work we focus on the propagation of EM waves in the frequency range from 100 Hz to 10 000 Hz within the region of the inner magnetosphere. We use a numerical procedure which performs ray tracing simu- lations and finds the wave trajectory along with other wave properties. Using these simulations we study propagation properties of equatorial noise emissions. Another subject of this work is development of a propagation scheme explaining a conjugate observation of quasiperiodic emissions by the Van Allen Probe A (VAP-A) spacecraft and the ground station in Athabasca. In this case we make use of a density distribution model based on measurements of plasmaspheric electron density done by the EMFISIS instrument onboard VAP-A.

Nelineární procesy v kosmickém plazmatu a jejich vliv na generování a šíření elektromagnetických vln

Nonlinear interactions of charged particles and large-amplitude waves have a signif- icant impact on magnetospheric dynamics. Here we focus on the cyclotron resonant interaction between energetic electrons and the discrete, whistler-mode chorus emissions in the Earth's outer radiation belt. The subject is introduced by an extensive review of whistler-mode dispersion properties, resonant electron trajectories and nonlinear wave- growth theories. We then present a new semi-empirical model of rising-tone chorus emis- sions with a fine subpacket structure. The model is then used in test-particle simulations to investigate nonlinear perturbations in hot electron distributions. Based on changes in electron fluxes, we estimate the resolution of spacecraft particle detectors required to detect the predicted perturbations. The test-particle method is further used to sim- ulate atmospheric precipitation of electrons caused by interaction with a single chorus wavepacket, and the result is put into connection with microbursts and pulsating auro- ras. We also detected a violation of the strong diffusion limit by the cyclotron resonant interaction, resulting in loss cone overfilling. 1Nelineární interakce nabitých částic a vln s vysokou amplitudou se významně proje- vují v dynamice magnetosfér. Zde se zaměřujeme na cyklotronovou rezonanční interakci mezi energetickými elektrony a diskrétními emisemi hvizdového módu zvanými chorus, jež se vyskytují ve vnějším radiačním pásu Země. Téma je uvedeno detailním rozborem disperzních vlastností hvizdových vln, trajektorií částic a přehledem teorií nelineárního růstu vln. V hlavní části prezentujeme nový semi-empirický model vlnových balíků choru s rostoucí frekvencí, které v sobě zahrnují jemné modulace amplitudy. Tento model je po- užit pro simulace testovacích částic, pomocí nichž studujeme nelineární perturbace v roz- dělení horkých elektronů. Na základě pozorovaných změn v toku elektronů jsme odhadli rozlišení částicových přístrojů potřebné k detekci předpovězených perturbací. Částicové simulace jsou dále využity ke zkoumání vysypávání elektronů do atmosféry v důsledku interakce s balíky choru. Výsledky jsou dány do souvislosti s pozorováním mikroburstů a pulzujících polárních září. Zároveň jsme v simulacích zaznamenali překročení difúzního limitu způsobené cyklotronovou interakcí, jež se projevilo přeplněním ztrátového kuželu. 1Department of Surface and Plasma ScienceKatedra fyziky povrchů a plazmatuFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult