Дисертації з теми "Alfevn Waves"
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Dong, Chuanfei. "Heating of ions by low-frequency Alfven waves in solar atmosphere." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37160.
Повний текст джерелаBetti, Riccardo. "Kinetic effects on global Alfvén waves." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/32129.
Повний текст джерелаCompton, Christopher S. "Propagation of Alfvén waves in the WVU HELIX device." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4525.
Повний текст джерелаTitle from document title page. Document formatted into pages; contains iv, 22 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 22).
Ivchenko, Nickolay. "Alfven Waves and Spatio-Temporal Structuring in the Auroral Ionosphere." Doctoral thesis, KTH, Alfvénlaboratoriet, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3364.
Повний текст джерелаPinches, Simon David. "Nonlinear interaction of fast particles with Alfven waves in tokamaks." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362917.
Повний текст джерелаManrique, Marcos Antonio Albarracin. "Plasma Diasnostic in Tokamaks Using Alfvén Waves." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-14082015-110334/.
Повний текст джерелаNeste trabalho é investigada a excitação de modos própios de Alfvén em tokamaks, utilizando antenas externas à coluna de plasma. A teoria básica das ondas de Alfvén é revista, incluindo efeitos não ideais, como resistividade. A seguir, o modelo teórico para excitação de ondas de Alfvén numa coluna cilindrica de plasma, desenvolvido por Kurt Appert, é apresentado em detalhe, como introdução ao problema mais complexo de ondas de Alfvén em plasmas toroidais. O modelo cilindrico é implementado em um código numérico, que é utilizado para estudar a excitação de modos globais de Alfvén (GAWs - Global Alfvén Waves), abaixo do chamado Continuo de Alfvén, nos tokamaks TCABR e JET, utilizando uma descrição realista de seus sistemas de antenas. A seguir é feita uma breve descrição dos auto modos toroidais de Alfvén (TAEs - Toroidal Alfvén Eigenmodes) que são excitados nas brechas do Continuo de Alfvén criadas pela condição de periodicidade em configurações toroidais. A excitação desses modos no tokamak JET é estudada utilizando os códigos HELENA, para reconstrução do equilíbrio magneto-hidrodinâmico, e CASTOR, que calcula os campos perturbados nesse equilíbrio, associados a instabilidades ou modos excitados, dentro do modelo magneto-hidrodinâmico resistivo. Esse estudo foi feito com o objetivo de determinar, de forma consistente, a qualidade do espectro e as auto-funções associadas a TAEs, com diferentes números toroidais n, excitados pelo atual sistema de antenas do JET. Em particular, foi investigado em detalhe o efeito das fases das correntes de alimentação dos diferentes módulos (oito) do sistema de antenas na qualidade do espectro excitado, utilizando um método original, implementado neste trabalho, de utilizar o código CASTOR. Os resultados indicam que embora a excitação de um determinado modo possa ser privilegiado por uma escolha ótima das fases, modos satélites também podem ser excitados com maior amplitude, de modo que a pureza do espectro não é substancialmente melhorada. Este é o principal resultado obtido neste trabalho.
Cox, Grace Alexandra. "Torsional Alfvén waves in the Earth's core." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9973/.
Повний текст джерелаPatrick, Antolin Tobos. "Predicting observational signatures of coronal heating by Alfven waves and nanoflares." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/126571.
Повний текст джерела0048
新制・課程博士
博士(理学)
甲第14894号
理博第3463号
新制||理||1507(附属図書館)
27332
UT51-2009-M808
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)教授 柴田 一成, 教授 一本 潔, 教授 嶺重 慎
学位規則第4条第1項該当
Khotyaintsev, Yuri. "Alfvén Waves and Energy Transformation in Space Plasmas." Doctoral thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3264.
Повний текст джерелаMartin, Clare E. "Alfvén waves in low-mass star-forming regions." Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14190.
Повний текст джерелаRussell, Alexander J. B. "Coupling of the solar wind, magnetosphere and ionosphere by MHD waves." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/2571.
Повний текст джерелаBrugman, Brian Thomas. "An investigation of the nonlinear interaction of Alfvén waves." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1459917811&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Повний текст джерелаSchäfer, Sebastian. "Spatial and temporal structure of Alvén resonator waves at the terrestrial Plasmapause." [Katlenburg-Lindau] Copernicus Publ, 2008. http://d-nb.info/993339034/04.
Повний текст джерелаVerwichte, Erwin Andre Omer. "Aspects of nonlinearity and dissipation in magnetohydrodynamics." Thesis, Open University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326565.
Повний текст джерелаSimpson, David. "Absolute and convective instabilities of circularly polarized AlfveÌn waves." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425186.
Повний текст джерелаNielson, Kevin Derek. "Analysis and gyrokinetic simulation of MHD Alfvén wave interactions." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3504.
Повний текст джерелаSchroeder, James William Ryan. "Exploring the Alfvén-wave acceleration of auroral electrons in the laboratory." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5846.
Повний текст джерелаVoronkov, Igor. "Shear Alfvén waves and shear flow instabilities in the Earth's magnetosphere." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0003/NQ34851.pdf.
Повний текст джерелаLilley, Matthew Keith. "Resonant interaction of fast particles with Alfvén waves in spherical tokamaks." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5487.
Повний текст джерелаMatsumoto, Takuma. "Spicule Formation, Coronal Heating, and Solar Wind Acceleration with Alfven waves driven by observed photospheric motions." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120664.
Повний текст джерелаShigueoka, Hisataki. "Estudo espectral das ondas de Alfvén em plasma cilíndrico." Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-04092012-113407/.
Повний текст джерелаThe spectrum of the ideal MHD waves in cylindrical plasmas has been studied. Assuming non homogeneous plasma, the spectrum presents the discrete and continuum (slow and Alfvén waves) regions. The eigenfunctions of the discrete regions are the solutions of the Hain-Lüst equation. In the continua, the solutions of this equation have singularities. It has been determined analytical expressions for the discrete eigenfunctions. These happen to be the Bessel\'s function and its eigenvalues agree with the numerical calculations. The discrete modes (global modes) of Alfvén waves have been calculated by numerically using the equilibrium configuration of tokamaks, beta < 1, and it was observed that these modes present a small contribution from the compressional waves. An analysis of the energy propagation was done using the Poynting vector. This has its importance in the problem of plasma heating by Alfvén waves. Its polarization was also studied. The effect of beta, through values greater than 1, was also studied. This condition is more aplicable to the spacial plasma problems, for example, in the solar photosphere\'s plasma. It has been calculated, for the first time, the discrete modes of slow waves, proposed theoretically. Its solutions (eigenfunctions and eigenvalues) have also the characteristics of the global modes, called global discrete slow waves. The study of spectral problems for the Reversed Field Pinch configurations was also determined here for both Sturmian eigenmodes for the Alfvén waves and Anti-Sturmian eigenmodes for the slow waves.
Thuecks, Derek Jon. "Laboratory investigations of dispersive Alfvén waves and their role in electron acceleration." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/268.
Повний текст джерелаFeher, Tamas Bela [Verfasser]. "Simulation of the interaction between Alfvén waves and fast particles / Tamas Bela Feher." Greifswald : Universitätsbibliothek Greifswald, 2014. http://d-nb.info/1048536556/34.
Повний текст джерелаOzeke, Louis Godwin. "Modelling the generation and properties of guided AlfveÌn waves in the magnetosphere." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273889.
Повний текст джерелаPuglia, Paulo Giovane Paschoali Pereira. "Excitação de ondas de helicon e de Alfvén em tokamak TCABR." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-30092011-155130/.
Повний текст джерелаThe objective of this work is to investigate the excitation of waves in a plasma using an antenna and to analyse the Alfvén resonances found. The Alfvén antenna heating system of the TCABR tokamak was designed to heat the plasma due to resonances. As the diodes of the toroidal field had burned down we used cleaning discharges, with low toroidal magnetic field, to test the excitation method and the identification of plasma resonances. With the demodulator circuit we measured helicon waves excited with the Alfv en antenna in the cleaning plasma using Langmuir and magnetic probes. With computational simulation we found the measured waves. A generator of variable frequency was used in this experiment. Both equipments are prepared for future experiments with the typical plasma of the TCABR, which has higher density than the cleaning plasma. This work was aimed to test to the demodulator circuit and the variable frequency generator, the data obtained were compared to that of a high sampling frequency oscilloscope. It is presented the description of the TCABR equipments used, antenna, magnetic probe, variable frequency generator of low power, demodulator circuit, Langmuir probe and a reflectometer which has a high sampling frequency (200MHZ) and frequency scanning in the range 18 40GHz, and was built in Portugal. In order to have a model of Alfv en resonances we calculated the plasma dieletric tensor both in the kinetic and magnetohydrodynamic limits. With computational simulation and using a two uid model, protons and electrons, it is possible to find some of the excited waves in the plasma and its dispersion relation, we calculated the fast magnetosonic wave and the global Alfvén wave. We found the radial position of the electromagnetic fields in the plasma. With the re ectometer we measured resonances of Alfvén waves induced by the antenna at the plasma border in a typical TCABR tokamak plasma discharge, with higher density and a high power fixed frequency generator. We used sidebands as a method to find out the resonances in the reflectometer data. These sidebands are localized around the resonance frequency, which is the Alfvén wave generator frequency. The sidebands were analysed with spectrograms of the data. The waves excited at the plasma border were also found in the simulation. The analysis results show that we could detect the plasma waves excited with the antennas. The demodulator circuit along with magnetic probes and the reflectometer can be used to find plasma resonances.
Guidolin, Luiz Carlos Büttner Mostaço. "Determinação da configuração de ondas de alfvén excitadas no tokamak TCABR." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-23042009-230419/.
Повний текст джерелаIn order to enhance the efficiency of the TCABR\'s Alfvén waves heating system, called AWES - Alfvén Waves Excitement System a diagnostics for determining the radio-frequency power applied to the plasma and a processing circuit for the magnetic coil system was built, characterized, installed and put into operation. The RF diagnostics system was designed to determine the total power that the set of AWES antennas applies to the plasma and, the magnetic coils system is designed to determine the RF spectrum excited by these antennas. Since the magnetic coils are already installed inside the TCABRs vacuum chamber only the signal processing circuit was built for it. The RF power diagnostics set is composed of three devices which are, one RF current sensing device, a set for determining the RF voltage and a multiplying system. A Rogowski coil is used for measuring the RF current. The RF voltage system may be split in two: a couple of voltage dividers and a processing circuit for the potential difference determination. Applying the RF current and voltage signals to the multiplier circuit it is possible to determine the RF power fed to the plasma. In this work a total of ten Rogowski coils, with 18mV/A sensibility constant, as well as twelve voltage dividers, capable of reducing a 10kV signal to approximately 5V signal, six voltage processing circuits and four signal multipliers, were built. Besides that, one demodulator circuit, capable of processing, simultaneously, the signals from four magnetic coils, was built too. All the devices constructed in this project were designed to be able to process signals with frequencies in the range of 3 to 6M Hz and produce a low frequency result signal that may be acquired automatically by the TCABR data acquisition system called TCAqs. For the calibration procedures and operational tests of the equipments developed in this work, it was established an Automated Calibration System (SCA) with a software application as one of its components that is capable of communicating and controlling test instruments, like oscilloscopes and function generators, through the communication port RS-232 and SCPI language. This software, called SCO, was fully developed using free and open source software in order to be used in Unix-Like operational systems like GNU/Linux. As a free software SCO was registered under the GNU/GPL license. The calibration procedures once operating with this system, whose principal characteristics is its automation functionality, allowed us to acquire a great quantity of data, that would have not been possible or practical to do manually. As a consequence, the resulting calibration curves may be considered more accurate, from an statistical point of view which enhanced considerably the quality of the results. After the characterization and detailed tests of all these devices off the TCABR and after the installation of the diagnostics in the TCABR, we may finally conclude they are ready to be used in experimental campaign.
Gonçalves, Diego Antonio Falceta. ""Plasmas empoeirados: ventos estelares e o meio interestelar"." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-10082006-193654/.
Повний текст джерелаIn this work, we firstly discuss the propagation of Alfvén waves in dusty plasmas found in several astrophysical environments. The wave dispersion relation is modified giving rise to new damping mechanisms. There are in the literature observational data indicating the presence of dust near the surface of cool giant and supergiant stars. We developed a stellar mass loss model where we show that a flux of Alfvén waves, damped by the dust presence,can generate a low velocity and high mass loss rate wind, in agreement with the observations. In the case of hot stars we show how it is possible to obtain the special conditions for dust growth in a wind collision model of massive binary systems. For this model it is possible to explain both, the high X-rays emissions and dust growth at the post-shock phase. Applying the idea to the $eta$ Carinae binary system, the model allows the determination of the system orbital and the stellar wind parameters. The stellar wind´s dust is then ejected to the interstellar medium. In a semi-empirical calculation we showed the importance of each stellar mass, at each evolutionary phase, on the dust feedback of the ISM. For star formation regions, we investigate the role of Alfvén waves, damped by the dust presence, on the stability of the molecular clouds. In spite of the works found in the literature, we showed that a dwarf molecular cloud, magnetically supported only, is unstable.
Puglia, Paulo Giovane Paschoali Pereira. "Identificação e localização de ondas de Alfvén excitadas no plasma de um tokamak." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-24092015-141928/.
Повний текст джерелаThe goal of this study is experimental detection of global Alfvén waves in the plasma of TCABR tokamak for diagnostic. The waves are excited by the use of one or two antennas posed within the shadow of the limiter within the TCABR vessel. To excite the global Alfvén eigenmode the antennas are fed with radio-frequency current of up to $ 15$A each, in the frequency range of $ 2-4 $ MHz. The presented scheme allows us to estimate the value of the effective mass in the centre of the plasma, which has its value affected by the concentration of impurities in the plasma. The amplifier of the antenna current is based on electronically switching MOSFETs. The waves are excited in the plasma with low power, thus it does not cause perturbation of the basic plasma parameters. The variation of the resonance frequency of the global Alfvén eigenmode with density is verified. The location of the resonance is identified in the central part of the plasma due to the wave amplitude beating with sawtooth oscillations, so that the phase inversion between the beating and the sawtooth oscillation improves the accuracy of determining the resonant condition. The toroidal parity of the excited modes is determined with use of two antennas oppositely located within the TCABR chamber and established by phase difference between their radio-frequency current. Knowledge of the toroidal wave number is important for a correct estimate of both the excited mode location and the plasma effective ion mass value. The value of the initially found effective mass was $ A_ {eff} \\approx 1.60$, higher than our expectations at first and did not agree with plasma conductivity estimates, and we proposed that it had a systematic error of approximately $10\\%$. To calibrate the central plasma density, it was used data from a reflectometer and some plasma discharges performed with helium gas, which has the same effective mass as most TCABR impurities. Finally, we estimate the effective mass as $ A_ {eff} = 1.40 \\pm 0.07$, that is consistent with the $ Z_ {eff} $ estimation.
Souza, Fábio Camilo de. "Teoria de ondas em Tokamaks." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-20092016-141959/.
Повний текст джерелаThis work intends to present a theorical treatment of Alfven and geodesic wave behavior in tokamak plasma, showing their function on the viability study for the construction of a fusion reactor for energy production. The Tokamak is a toroidal chamber where the plasma stays confined under effects of a strong magnetic field where its can reach high temperature in necessary conditions for nuclear fusion. It is presented the behavior of Alfvén waves and deeper Geodesic Acoustic Modes. For Alfvén waves, it is described it\'s nature, a comum wave in any plasma under magnetic field, when properly perturbed, Alfvén waves can propagate on the magnetic field line, also it is presented possible applications. It\'s presented a theorical treatment where Alfvén modes in cilindrical coordinates, approximation for Tokamak with high aspect ratio. In Geodesic Acoustic Mode, GAM, driven by the todoidal curvature and symmetry of Tokamak, it is showed possible applications and a interaction with Alfvén waves. A perturbation that propagate in poloidal direction, symmetrical in toroidal direction, with toroidal number $N=0$ and poloidal number $M = 0, \\pm 1, \\pm 2 , ...$, a theorical treatment on rotation effects of electrons and ions in form of flux along the magnetic field line, on dispersion relation and instability of GAM is presented. In the end, it is presented a data analysis on COMPASS shoots, where is showed a possible qualitative correspondence between GAM dispersion and instabilities with the theory and experiment.
Chang, Ouliang. "Numerical Simulation of Ion-Cyclotron Turbulence Generated by Artificial Plasma Cloud Release." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34018.
Повний текст джерелаMaster of Science
Sakaue, Takahito. "Nonlinear Alfvén Wave Model for Solar/Stellar Chromosphere, Corona and Wind from the Sun to M Dwarfs." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263472.
Повний текст джерелаTholerus, Emmi. "The dynamics of Alfvén eigenmodes excited by energetic ions in toroidal plasmas." Licentiate thesis, KTH, Fusionsplasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163127.
Повний текст джерелаQC 20150330
Tholerus, Emmi. "The dynamics of Alfvén eigenmodes excited by energetic ions in toroidal plasmas." Doctoral thesis, KTH, Fusionsplasmafysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193029.
Повний текст джерелаDe framtida fusionskraftverken baserade på magnetisk inneslutning kommer att hantera plasmor som oundvikligen innehåller energetiska (icke-termiska) partiklar. Dessa partiklar kommer exempelvis från fusionsreaktioner eller från externa uppvärmningsmekanismer av plasmat. Ensembler av energetiska joner kan excitera egenmoder i Alfvén-frekvensområdet i en sådan utsträckning att de resulterande vågfälten omfördelar de energetiska jonerna i rummet, och potentiellt slungar ut jonerna ur plasmat. Omfördelningen av joner kan orsaka en väsentligen minskad uppvärmningseffekt. Det är nödvändigt att förstå dynamiken hos denna typ av instabilitet för att kunna optimera verkningsgraden hos experiment och hos framtida fusionskraftverk. Två modeller har utvecklats för att simulera interaktionen mellan energetiska joner och Alfvén-egenmoder. Den första är en bump-on-tail-modell, av vilken två versioner har utvecklats: en fullt icke-linjär och en kvasi-linjär. I den kvasi-linjära versionen har partiklarnas fasrum en lägre dimensionalitet än i den icke-linjära versionen. Till skillnad från tidigare liknande studier innehåller denna bump-on-tail-modell en dekorrelation av våg-partikelfasen för att modellera stokasticitet hos systemet. När den karakteristiska tidsskalan för makroskopisk fasdekorrelation är ungefär samma som eller kortare än tidsskalan för icke-linjär våg-partikeldynamik så stämmer den icke-linjära och den kvasi-linjära beskrivningen överens kvantitativt. En ändlig fasdekorrelation förändrar vågmodens tillväxthastighet och satureringsamplitud i system med en inverterad energifördelning omkring våg-partikelresonansen. Analytiska uttryck för korrektionen av tillväxthastigheten och satureringsamplituden har härletts, vilka stämmer väl överens med numeriska simuleringar. En relativt svag fasdekorrelation försvagar även "frequency chirping events" (snabba frekvensskiftningar i korttids-Fourier-transformen av egenmodens amplitudutveckling) hos egenmoden. Den andra modellen, kallad FOXTAIL, har ett mycket bredare giltighetsområde än bump-on-tail-modellen. FOXTAIL kan simulera system med flera egenmoder, och den inkluderar effekter av olika enskilda partikelbanor relativt vågfälten. Simuleringar med FOXTAIL och med bump-on-tail-modellen har jämförts för att kvantitativt bestämma bump-on-tail-modellens giltighetsområde. Studier av scenarier med två egenmoder bekräftar de förväntade effekterna av när Chirikov-kriteriet för resonansöverlapp uppfylls. Även inflytandet av ICRH på dynamiken mellan egenmoder och energetiska joner har studerats, vilket har visat kvalitativt liknande effekter som har observerats i närvaron av fasdekorrelation. En annan modell, vilken beskriver effektiviteten hos "fast wave current drive" (strömdrivning med snabba magnetosoniska vågor), har utvecklats för att studera inflytandet av passiva komponenter nära antennen, i vilka strömmar kan induceras av vågfälten som genereras av antennen. Det visades att den utskickade vågens direktivitet, medelvärdesbildat över modellparametrar, generellt sett minskade vid närvaron av passiva komponenter, förutom vid låg "sinlge pass damping" (dämpning av vågen vid propagering genom hela plasmat), då direktiviteten istället ökade något, men bytte tecken i toroidal riktning.
QC 20160927
Lee, Bo Ram Verfasser], Dieter [Akademischer Betreuer] [Hoffmann, and Christoph [Akademischer Betreuer] Niemann. "Study of a laser generated diamagnetic cavity and Alfvén waves in a large magnetized plasma / Bo Ram Lee. Betreuer: Dieter H. H. Hoffmann ; Christoph Niemann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1112044752/34.
Повний текст джерелаLee, Bo Ram [Verfasser], Dieter [Akademischer Betreuer] Hoffmann, and Christoph [Akademischer Betreuer] Niemann. "Study of a laser generated diamagnetic cavity and Alfvén waves in a large magnetized plasma / Bo Ram Lee. Betreuer: Dieter H. H. Hoffmann ; Christoph Niemann." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-52112.
Повний текст джерелаSchreiner, Anne [Verfasser], and Joachim [Gutachter] Saur. "A Model for Dissipation of Solar Wind Turbulence with Damping by Kinetic Alfvén Waves: Comparison with Observations and Implications for the Dissipation Process in the Solar Wind / Anne Schreiner ; Gutachter: Joachim Saur." Köln : Universitäts- und Stadtbibliothek Köln, 2017. http://d-nb.info/113762423X/34.
Повний текст джерелаEilers, Bischoff Jens, and Sebastian Jovancic. "Variability of Io’s Aurora and the Moon’s Footprint on Jupiter." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293888.
Повний текст джерелаVi studerar hur intensiteten av Ios aurora varierar i relation till Jupiters rotation mätt i system III longitud. Ios aurora mättes inom UVC området av Hubble Space Telescope (HST) med FUV-MAMA fotondetektorn. Matlab användes för att filtrera bort oönskade signaler som reflektion och bakgrund samt ta hänsyn till sensorns optiska system. Observationsområderna på sensorn konstruerades för mätningen av syre OI (1356Å ) och svavel SI (1479Å ) emissionerna. Genom att sampla fo- tondetektioner inom varje observationsområde så rekonstruerar vi en intensitetskurva som vi mappar till system III longitud. En kurva var sedan anpassad till rekonstruktionen med hjälp av en sinusanpassning. Resultaten visar två intensitetstoppar vid system III longituderna (140 ± 5)◦ och (284 ± 2)◦ för både OI och SI . Kvoten mellan topparna var (38 ± 6)% för OI och (28 ± 6)% för SI . Skillnaden i topparna kan förklaras av att sannolikheten att excitera svavel är större än att excitera syre. För fullständig beskrivning av skillnaden i topparna skulle mätningar av syre till svavel proportionen i Ios atmosfär behövas. Vi jämför våra reslutat med mätningar av Ios avtryck på Jupiter från JUNO och andra HST mätningar. Vi finner det sannolikt att vi bekräftar ytterligare varians i topparnas vinkel, främst för den första toppen vars vinkel är signifikant större. Variationer i Jupiters magnetfält och plasmadensitet av Jupiters plasmatorid kan sannolikt förklara positionen av topparna och intensitetsvariationerna. Vidare forskning behövs för att utförligt förklara dessa mekanismer.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
Vedin, Jörgen. "Numerical modeling of auroral processes." Doctoral thesis, Umeå University, Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1117.
Повний текст джерелаOne of the most conspicuous problems in space physics for the last decades has been to theoretically describe how the large parallel electric fields on auroral field lines can be generated. There is strong observational evidence of such electric fields, and stationary theory supports the need for electric fields accelerating electrons to the ionosphere where they generate auroras. However, dynamic models have not been able to reproduce these electric fields. This thesis sheds some light on this incompatibility and shows that the missing ingredient in previous dynamic models is a correct description of the electron temperature. As the electrons accelerate towards the ionosphere, their velocity along the magnetic field line will increase. In the converging magnetic field lines, the mirror force will convert much of the parallel velocity into perpendicular velocity. The result of the acceleration and mirroring will be a velocity distribution with a significantly higher temperature in the auroral acceleration region than above. The enhanced temperature corresponds to strong electron pressure gradients that balance the parallel electric fields. Thus, in regions with electron acceleration along converging magnetic field lines, the electron temperature increase is a fundamental process and must be included in any model that aims to describe the build up of parallel electric fields. The development of such a model has been hampered by the difficulty to describe the temperature variation. This thesis shows that a local equation of state cannot be used, but the electron temperature variations must be descibed as a nonlocal response to the state of the auroral flux tube. The nonlocal response can be accomplished by the particle-fluid model presented in this thesis. This new dynamic model is a combination of a fluid model and a Particle-In-Cell (PIC) model and results in large parallel electric fields consistent with in-situ observations.
Blanco-Benavides, Jose Mauricio. "Electron acceleration by Inertial Alfven Waves." Master's thesis, 2011. http://hdl.handle.net/10048/1786.
Повний текст джерелаKortbawi, David. "Alfven wave studies on a tokamak." 1987. http://catalog.hathitrust.org/api/volumes/oclc/17852866.html.
Повний текст джерелаHirsch, Michael. "Alfvén waves underlying ionospheric destabilization: ground-based observations." Thesis, 2017. https://hdl.handle.net/2144/23382.
Повний текст джерелаGhanesh, N. "MHD Waves Driven by Small-scale Motion and Implications for the Earth's Core." Thesis, 2017. http://etd.iisc.ernet.in/2005/3580.
Повний текст джерелаThuecks, Derek Jon Kletzing Craig A. "Laboratory investigations of dispersive Alfvén waves and their role in electron acceleration." 2009. http://ir.uiowa.edu/etd/268/.
Повний текст джерелаSedeh, Leila Norouzi. "Doppler clutter in HF radar systems produced by ULF waves." Thesis, 2014. http://hdl.handle.net/1959.13/1042283.
Повний текст джерелаUltra low frequency (ULF) waves are generated by the interaction of the solar wind with Earth’s magnetosphere. The waves propagate through the ionosphere and may be seen in data from SuperDARN Over-The-Horizon radars as oscillations in Doppler velocity which coincide with oscillations of the geomagnetic field recorded by ground magnetometers. Data from the two Tasman International Geospace Environment Radars (TIGER) and the magnetometer located on Macquarie Island over 2006-2009 show that ULF wave signatures are common. The dependence with time of day showed most ULF radar events occurred between 6-12 UT (dusk and pre-mid-night sector). Using the Maximum Entropy Method (MEM) several spectral aspects of detected ULF waves were investigated for the first time. Most of the recorded frequencies were in the range 1- 4 mHz. Some frequencies were seen more often than others with the more common frequencies spaced about 0.3mHz apart, consistent with previous studies. There was no evidence of a frequency dependence on latitude. Field line resonance (FLR) signatures in the radar data were expected but were not common, as shown by comparisons with coincident ground magnetometer data. This study has shown that most radar echoes containing ULF wave Doppler signatures appear to be backscattered from the plasmapause region mapped into the ionosphere. Modelling of the Doppler velocity combined with a ULF wave model and two dimensional ray tracing was achieved for the first time. The results are consistent with experimental observations. With further improvement, this modelling should provide a valuable tool to understand shear Alfven mode and fast mode plasma wave interactions within the ionosphere and their effects on HF propagation through the ionosphere.
Jaafari, Fajer Bitar. "Simulations of high-latitude ionosphere-magnetosphere region plasma density structures and the Alfven waves effects." 2009. http://hdl.handle.net/10106/1755.
Повний текст джерелаChen, Ching-Chung, and 陳敬中. "A Simulation Study of Rotational Discontinuities and Nonlinear Alfven Waves in the Solar Wind." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/534gks.
Повний текст джерела國立中央大學
太空科學研究所
94
This thesis work studies rotational discontinuities (RDs) by means of electron-ion two-fluid simulation and hybrid simulation (fluid electrons and kinetic ions). We examine the evolution of RDs under different initial conditions. Our goal is to find the best initial conditions, which can yield the most stable RD structures. The results of this research show that, when the initial width of the RD transition region is less than 30 , short-wavelength and large-amplitude waves will be emitted from the transition region. As a result, the transition region widens gradually with time. The RD structure is relatively steady when the initial width of the RD is more than 90 , although it can still emit small-amplitude waves to both up-stream and down-stream sides. The width of the transition region keeps constant and becomes a stable hook-shaped rotational structure. Double-hook rotational structures and d-shaped rotational structures, which have never been obtained in the previous simulations, are found in this thesis study. The double-hook rotational structures obtained in this study are similar to the structures of RDs and Alfven waves observed in the solar wind.
莊宏親. "He++ Acceleration by Alfven Waves in the Solar Wind: Formation of He++/H+ Differential Streams." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/40010200007931549912.
Повний текст джерелаWang, Ge active 2013. "Rapid frequency chirps of an Alfvén wave in a toroidal plasma." 2013. http://hdl.handle.net/2152/21380.
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Chen-JiaWeng and 翁承嘉. "Effects of ion-neutral collisions on Alfvén waves and formation of compound discontinuity/shock structures." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/gcyyvt.
Повний текст джерела國立成功大學
物理學系碩博士班
101
Alfvén waves are low-frequency transverse waves propagating in a magnetized plasma. The presence of neutral particles may modify the wave frequency and cause damping of Alfvén waves. MHD discontinuity is a stationary thin layer through which the magnetic field, plasma density, pressure, and flow velocity may have a significant jump. In the first part of this thesis, we investigate the effect of ion-neutral collisions on the damping of Alfvén waves in a homogeneous plasma. In the second part of this thesis, 1-D Riemann problem is used to study the generation and evolution of MHD discontinuities associated with magnetic reconnection. First, the effects on Alfvén waves depend on two parameters: (1) , the ratio of neutral density and ion density , and (2) , the ratio of neutral collisional frequency by ions , , to the wave frequency . Most of previous studies examined only the limiting case with a relatively large neutral collisional frequency or . In the Chapter 2 of this thesis, the dispersion relation for Alfvén waves is solved for all values of and . It is found for the first time that there is a “forbidden zone” in the parameter space, where the real frequency of Alfvén waves becomes zero and Alfvén waves become evanescent. Approximate solutions in the limit as well as are obtained. We also discuss the propagation and damping of Alfvén waves in the ionosphere and in the solar chromosphere, where the “forbidden zone” is identified. Second, we use 1-D hybrid code to simulate the generation and evolution of MHD discontinuities associated with magnetic reconnection in a current sheet. As a result of the leakage of slow shock (SS), the ion parallel temperature and temperature anisotropy tends to increase, where is the ion parallel (perpendicular) beta. The propagation rotational discontinuity (RD) and slow shock (SS) lead to formation of various compound structures in the reconnection outflow region. Four types of compound structure are found in our simulations: (a) RD-SS compound structure: the RD is attached to the leading part of SS, (b) SS-RD (DD) compound structure: RD is attached to the rear part of SS, (c) SS-RD-SS compound structure: RD is trapped inside SS, and (d) switch-off slow shock (SSS) with a rotational wave train. The type of compound structure generated depends on the initial ion beta and magnetic shear angle .
Lee, Bo Ram. "Study of a laser generated diamagnetic cavity and Alfvén waves in a large magnetized plasma." Phd thesis, 2015. https://tuprints.ulb.tu-darmstadt.de/5211/1/Diss_ver111_final.pdf.
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