Дисертації з теми "Auroral plasma"
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Liléo, Sónia. "Auroral electrodynamics of plasma boundary regions." Doctoral thesis, KTH, Rymd- och plasmafysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10446.
Повний текст джерелаQC 20100727
Schlatter, Nicola. "Radar Signatures of Auroral Plasma Instability." Doctoral thesis, KTH, Rymd- och plasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160894.
Повний текст джерелаQC 20150303
Liléo, Sónia. "Auroral electrodynamics of plasma boundary regions /." Stockholm : Skolan för elektro- och systemteknik, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10446.
Повний текст джерелаDreyer, Joshua. "A detailed study of auroral fragments." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388546.
Повний текст джерелаVedin, 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.
Schroeder, 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 джерелаEliasson, Lars. "Satellite observations of auroral acceleration processes." Doctoral thesis, Umeå universitet, Rymdfysik, 1994. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-102339.
Повний текст джерелаDiss. (sammanfattning) Umeå : Umeå universitet, 1994, härtill 6 uppsatser.
digitalisering@umu.se
Fillingim, Matthew Owen. "Kinetic processes in the plasma sheet observed during auroral activity /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/6824.
Повний текст джерелаKalmoni, N. M. E. "The role of magnetospheric plasma instabilities in auroral and substorm dynamics." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1546163/.
Повний текст джерелаKopf, Andrew James. "A multi-instrument study of auroral hiss at Saturn." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/692.
Повний текст джерелаMain, Daniel S. "Multi-ion plasma processes in the low altitude auroral upward current region." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3207758.
Повний текст джерелаDel, Pozo Carlos F. (Carlos Federico). "440 MHz radar observations of plasma turbulence in the auroral lower ionosphere." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/17235.
Повний текст джерелаIncludes bibliographical references (p. 274-287).
by Carlos F. del Pozo.
Ph.D.
Mottez, Fabrice. "Effets des ondes cyclotroniques ioniques sur le plasma auroral : striation du plasma et production de doubles couches faibles." Paris 11, 1991. http://www.theses.fr/1991PA112123.
Повний текст джерелаBrändström, Urban. "The Auroral Large Imaging System : design, operation and scientific results." Doctoral thesis, Umeå University, Space Science, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-36.
Повний текст джерелаThe Auroral Large Imaging System (ALIS) was proposed in 1989 by Åke Steen as a joint Scandinavian ground-based nework of automated auroral imaging stations. The primary scientic objective was in the field of auroral physics, but it was soon realised that ALIS could be used in other fields, for example, studies of Polar Stratospheric Clouds (PSC), meteors, as well as other atmospheric phenomena.
This report describes the design, operation and scientic results from a Swedish prototype of ALIS consisting of six unmanned remote-controlled stations located in a grid of about 50 km in northern Sweden. Each station is equipped with a sensitive high-resolution (1024 x 1024 pixels) unintensified monochromatic CCDimager. A six-position filter-wheel for narrow-band interference filters facilitates absolute spectroscopic measurements of, for example, auroral and airglow emissions. Overlapping fields-of-view resulting from the station baseline of about 50 km combined with the station field-of-view of 50° to 60°, enable triangulation as well as tomographic methods to be employed for obtaining altitude information of the observed phenomena.
ALIS was probably one of the first instruments to take advantage of unintensi- fied (i.e. no image-intensifier) scientific-grade CCDs as detectors for spectroscopic imaging studies with multiple stations of faint phenomena such as aurora, airglow, etc. This makes absolute calibration a task that is as important as it is dificult.
Although ALIS was primarily designed for auroral studies, the majority of the scientific results so far have, quite unexpectedly, been obtained from observations of HF pump-enhanced airglow (recently renamed Radio-Induced Aurora). ALIS made the first unambiguous observation of this phenomena at high-latitudes and the first tomography-like inversion of height profiles of the airglow regions. The scientific results so far include tomographic estimates of the auroral electron spectra, coordinated observations with satellite and radar, as well as studies of polar stratospheric clouds. An ALIS imager also participated in a joint project that produced the first ground-based daytime auroral images. Recently ALIS made spectroscopic observations of a Leonid meteor-trail and preliminary analysis indicates the possible detection of water in the Leonid.
Sullivan, Joanna Mary. "Spectral studies of small-scale auroral structure and plasma instability in the high-latitude ionosphere." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65694/.
Повний текст джерелаSewell, Stephen. "Efficient particle-in-cell simulation of auroral plasma phenomena using a CUDA enabled graphics processing unit." Thesis, The University of Alabama in Huntsville, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1559557.
Повний текст джерелаThis thesis introduces a software framework that effectively utilizes low-cost commercially available Graphic Processing Units (GPUs) to simulate complex scientific plasma phenomena that are modeled using the Particle-In-Cell (PIC) paradigm. The software framework that was developed conforms to the Compute Unified Device Architecture (CUDA), a standard for general purpose graphic processing that was introduced by NVIDIA Corporation. This framework has been verified for correctness and applied to advance the state of understanding of the electromagnetic aspects of the development of the Aurora Borealis and Aurora Australis.
For each phase of the PIC methodology, this research has identified one or more methods to exploit the problem's natural parallelism and effectively map it for execution on the graphic processing unit and its host processor. The sources of overhead that can reduce the effectiveness of parallelization for each of these methods have also been identified. One of the novel aspects of this research was the utilization of particle sorting during the grid interpolation phase. The final representation resulted in simulations that executed about 38 times faster than simulations that were run on a single-core general-purpose processing system. The scalability of this framework to larger problem sizes and future generation systems has also been investigated.
Stenberg, Gabriella. "The importance of waves in space plasmas : Examples from the auroral region and the magnetopause." Doctoral thesis, Umeå University, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-538.
Повний текст джерелаThis thesis discusses the reasons for space exploration and space science. Space plasma physics is identified as an essential building block to understand the space environment and it is argued that observation and analysis of space plasma waves is an important approach.
Space plasma waves are the main actors in many important processes. So-called broadband waves are found responsible for much of the ion heating in the auroral region. We investigate the wave properties of broadband waves and show that they can be described as a mixture of electrostatic wave modes. In small regions void of cold electrons the broadband activity is found to be ion acoustic waves and these regions are also identified as acceleration regions. The identification of the wave modes includes reconstructions of the wave distribution function. The reconstruction technique allow us to determine the wave vector spectrum, which cannot be measured directly. The method is applied to other wave events and it is compared in some detail with a similar method.
Space plasma wave are also sensitive tools for investigations of both the fine-structure and the dynamics of space plasmas. Studies of whistler mode waves observed in the boundary layer on the magnetospheric side of the magnetopause reveal that the plasma is organized in tube-like structures moving with the plasma drift velocity. The perpendicular dimension of these tubes is of the order of the electron inertial length. We present evidence that each tube is linked to a reconnection site and argue that the high density of tube-like structures indicates patchy reconnection.
Backrud, Marie. "Cluster Observations and Theoretical Explanations of Broadband Waves in the Auroral Region." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5809.
Повний текст джерелаYajima, Akira. "Electrostatic particle simulations of the weak double layer in the auroral plasma including the effects of up-flowing ions." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150836.
Повний текст джерелаCavalcanti, Claudio Jose de Holanda. "Emissão, propagação e amplificação da radiação quilométrica das auroras nas subcavidades aurorais." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2001. http://hdl.handle.net/10183/31458.
Повний текст джерелаThe present work investigates the propagation and amplification of electromagnetic waves in a plasma localized in the vicinity of the geomagnetic poles, at heights not much greater than three times the Earth's radius. The phenomena studied is known as the Aurorai Kilometric Radiation (AKR), the strongest of the various types of emission that can occur as a consequence of the interaction of the solar wind and the terrestrial magnetosphere. Initially some of the main known characteristics of this emission are discussed, including a review of the literature on the observational features of the phenomena. The electron cyclotron maser mechanism is then discussed as a possible generator mechanism for the AKR. This mechanism is then utilized in order to study the propagation and amplification of the Aurorai Kilometric Radiation, the physical parameters necessary for this study being obtained from a physical model based in the work of Chiu & Schultz (1978), which approximately reproduces the plasma conditions in the source region. The model includes the gradients perpendicular to the ambient magnetic field, with small scale variations of the density, called auroral subcavities. The componente of the plasma dielectric tensor are calculated for one distribution which consists in a summation of a Maxwellian, which describes cold electrons, and a relativistic DGH distribution for the energetic loss-cone electrons, being used the locally homogeneous approximation. A ray-tracing study is done using the geometrical optics equations, and at each point along the wave trajectory the spectral emissivity is calculated. By means of the transfer equation, the wave amplification factor is obtained for as long as the wave propagates in the source region. It is verified that the inclusion of the emissivity of the medium in the ray tracing calculation enhances the amplification factor. However, the increase obtained is not sufficient to expiam the amplification leveis currently observed. On the other hand, it is concluded that the inclusion of small scale variations (in the direction perpendicular to the magnetic field) in the density and other plasma parameters in the source region, may be an important factor in the explanation of the observed amplification leveis.
Lamy, Laurent. "Etude des émissions radio aurorales de Saturne, modélisation et aurores UV." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00328763.
Повний текст джерелаEngwall, Erik. "Low-Energy Ion Escape from the Terrestrial Polar Regions." Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-100650.
Повний текст джерелаPalmer, Jonathan Richard. "Plasma density variations in the aurora." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262167.
Повний текст джерелаDahlgren, Hanna. "Multi-spectral analysis of fine scale aurora." Doctoral thesis, KTH, Rymd- och plasmafysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24907.
Повний текст джерелаQC 20101001
Wanzambi, Ellinor, and Maja Gustafsson. "Parallel currents in the magnetotail and their connection to aurora." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355621.
Повний текст джерелаPavan, Joel. "Efeitos de gradientes perpendiculares na amplificação da radiação quilométrica das auroras." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/11022.
Повний текст джерелаThe in uence from source region inhomogeneous character on ampli cation of Auroral Kilometric Radiation is investigated. Firstly, a review over relevant works published about the same general theme is made, concerning about observational data as well theoretical models and numerical simulations. This review is preceded by the establishment of de nitions and concepts related to the theme. Two distinct approaches are considered in determining the ampli cation of radiation across the source region. First approach takes the plasma as locally homogeneous, while second approach account, explicitly, for gradients on plasma parameters. The ampli cation is obtained through evaluation of the dielectric tensor and the evolution of radiation through ray tracing. Plasma parameters are obtained using a self-consistent formulation which account for an electric potential drop along geomagnetic eld lines. An auroral slab model is used where the ambient magnetic eld is taken as locally homogeneous. The subjacent theoretical model adopted is the electron-cyclotron maser. The main result obtained reveals a reduction on nal ampli cation by a factor about three, when plasma parameters gradients are explicitly accounted. This nding may have implications on capability of electron-cyclotron maser for explanation the most intense levels of radiation observed.
Hess, Sébastien. "Processus d'accélération et émissions radio dans le circuit Io-Jupiter." Paris 6, 2008. http://www.theses.fr/2008PA066051.
Повний текст джерелаGaelzer, Rudi. "O maser de elétron-cíclotron como mecanismo gerador da radiação quilométrica das auroras." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1991. http://hdl.handle.net/10183/132968.
Повний текст джерелаWe investigate the possibility of electromagnetic wave amplification in the plasma situated over the geomagnetic peles up to a height around five earth radii. In this region occurs the most intense wave emission phenomenon in the terrestrial magnetosphere, known as "Aurora! Kilometric Radiation", which is a consequence of the solar wind-magnetosphere interaction. Initially, we make a comprehensive review on the known observational characteristics of the phenomenon. Next, the electron-cyclotron maser is discussed as a possible generation mechanism for the phenomenon, anel a review is made on the most important theoretical works, which applied the maser in the complex frequency formulation. We then begin a study on the Auroral Kilometric Radiation applying the maser mechanism in its complex wave frequency formulation . The physical parameters needed for the calculations were obtained from a particular model, especially created to approximately reproduce the real conditions in the aurora! zone, taking into account even a particular density gradient, perpendicular to the geomagnetic field. The components of the dielectric tensor are calculated in the locally homogeneous plasma approximation and the electron distribution function is taken as the sum of a cold maxwellian plus a relativistic Dory-Guest-Harris distribuition. The dispersion relation is exactly solved with all harmonics and powers of Larmor radius needed for the convergency of the solutions. We have also clone ray-tracing studies in the geometrical opti cs approximation, using the Poeverlein's method. We have found Ll1at , wh en Lhe electronic plasma to cyclotron frequencies ratio is Wpe/De < 0.1, the waves t hat propagatc in the fast extraordinary mode are amplified at frequencies very near to Lhe c.\·c lot ron frequency anel in the quasi-perpendi cular direction of the geomagnetic field. On t.hc olhcr hand , c.v·PE/De > 0.1 , the component of the wave vector parallel to the magnet i c fi eld musL have larger values for the amplification to occur, progressively smaller in valu e. The ray-L racing st udies have shown that the spatial scale of the inhomogeneity, perp endi cular to the magnetic field , is a very important factor in the amplification, anel that the cli stance to obtain a given amplification can be substantially reduced when the clensity gra.client is increasecl.
Eilers, 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
Modin, Emelie. "Estimating Charging on a Sounding Rocket Experiment Using Plasma Simulation." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293892.
Повний текст джерелаSyftet med detta projekt är att modellera ström-pänningskaraktäristisk kurvor för olika plasmatillstånd som finns i aktiva auroror. Detta görs genom att simulera laddning på en FFU med en ansluten Langmuir-prob i SPIS. Dessa I-V-kurvor används för att bestämma plasma egenskaperna för aurororna sondraketerna SPIDER-1 och SPIDER- 2 skjöts upp i. I-V kurvorna används också för att bestämma hur plasma parametrarna elektron temperatur, jon temperatur och elektrondensitet samt hur probens geometri påverkar I-V- kurvornas utseende. Resultaten visade att den plasma SPIDER-1 blev uppskjuten i troligen hade nominella förhållanden och att den SPIDER-2 blev uppskjuten i troligtvis hade kallare elektroner. En slutsats om att endast elektron temperaturen påverkar formen på IV- kurvorna kan dras, såväl som slutsatsen att probens geometri inte påverkar formen på IV-kurvorna. Ett annat resultat visar att elektron temperaturen också påverkar ytpotentialen på FFUn. En högre elektron temperatur ger FFUn en mer negativ laddning.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
Hammarsten, Michael. "A statistical study of incoherent scatter plasma line enhancements during the International Polar Year ’07-’08 in Svalbard." Thesis, Luleå tekniska universitet, Rymdteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60158.
Повний текст джерелаBouhram, Mehdi. "Étude des échappements d'ions ionosphériques du côté jour des zones aurorales." Paris 6, 2002. http://www.theses.fr/2002PA066048.
Повний текст джерелаGénot, V. "Étude des phénomènes d'accélération de particules dans les régions aurorales des magnétosphères." Phd thesis, Université de Versailles-Saint Quentin en Yvelines, 1999. http://tel.archives-ouvertes.fr/tel-00010474.
Повний текст джерелаpeut être étudiée dans un laboratoire naturel : les régions aurorales de la
Terre, et plus globalement, celles des planètes magnétisées. Ces régions sont
en effet le siège de nombreux processus qui donnent, entre autres, naissance
aux aurores boréales et australes, phénomènes spectaculaires mais dont de
nombreux aspects restent incompris. En particulier, de multiples mesures de
satellites ont montré l'existence de populations de particules énergétiques
précipitant vers la Terre, nécessitant le maintien d'une différence de
potentiel électrique élevée que la plupart des modèles proposés sont incapables
de reproduire. D'une manière générale, comprendre l'accélération, c'est
comprendre une partie du couplage dynamique entre la magnétosphère, où
l'énergie est libérée lors des sous-orages, et l'ionosphère où l'énergie est
dissipée. L'étude de cette dissipation, qui opère sur de courtes échelles
spatiales et temporelles, constitue le thème principal de ce travail. Dans
ce but, nous considérons une perturbation électromagnétique, sous forme d'onde
d'Alfvén, se propageant le long des lignes de champ magnétique. Son
interaction, en région aurorale, avec les cavités de plasma, structures
fortement inhomogènes, conduit à l'apparition de champs électriques parallèles
susceptibles d'accélérer les particules, ainsi qu'à un transfert d'énergie
significatif des ondes vers les électrons. Finalement, cette étude permet de
dégager un nouveau scénario de formation des arcs auroraux. Ce travail a été
mené de façon analytique avant d'être traité numériquement grâce à un code
particulaire.
El-Alaoui, Mostafa. "Etude des faisceaux d'ions détectés en région aurorale par le satellite AUREOL-3 : synthèse des observations et apport de la modélisation numérique." Toulouse 3, 1994. http://www.theses.fr/1994TOU30037.
Повний текст джерелаPayan, Alexia Paule Marie-Renee. "Uncovering local magnetospheric processes governing the morphology and periodicity of Ganymede’s aurora using three-dimensional multifluid simulations of Ganymede’s magnetosphere." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51756.
Повний текст джерелаGarcia, Geraldine. "Etude de la dynamique des electrons en presence de fortes densites de courant." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00250116.
Повний текст джерелаAinsi, nous allons étudier la dynamique des électrons portant ces courants très intenses. Pour cela, nous considérons un ensemble d'électrons se déplaçant à travers un gaz ionosphérique d'ions et de neutres et soumis à un champ électrique aligné au champ magnétique. Nous avons développé un modèle cinétique de collisions, incluant les collisions électrons/électrons, électrons/ions et électrons/neutres. Nous utilisons une approche Fokker-Planck afin de décrire les collisions binaires entre les particules chargées (interactions à longue portée). L'opérateur de collisions comporte deux parties : l'équation de Langevin pour les collisions électrons/électrons et électrons/ions et la méthode de Monte-Carlo avec une approche "collision nulle" pour les collisions électrons/neutres. Nous donnons un exemple de retour à l'équilibre afin de tester ces opérateurs de collisions et d'étudier l'impact des différents termes (les collisions électrons/électrons et électrons/ions d'une part et les collisions électrons/neutres d'autre part).
Tout d'abord, nous considérons un champ électrique constant au cours du temps. Dans ce test, les électrons sont déplacés uniquement selon z, la direction parallèle au champ electrique et au champ magnétique. Nous constatons alors que les fonctions de distribution ne sont plus maxwelliennes et que des électrons runaway sont créés. Ces électrons représentent 20% de la densité totale et ce sont eux qui portent le courant. Cependant, nous remarquons que nous ne conservons pas la divergence du courant nulle.
Nous introduisons alors des modifications majeures telles qu'une rétroaction sur le champ électrique ou la résolution des équations fluides afin de tenir compte de l'évolution des moments de la fonction de distribution des ions. Nous observons que les fonctions de distribution des électrons restent non maxwelliennes. Des électrons suprathermiques sont créés et portent le courant. En effet, la population correspondant au coeur de la distribution reste au repos. Comme ces électrons subissent moins de collisions, ils augmentent la conductivité du plasma.
Enfin, nous avons réalisé une étude paramétrique afin d'étudier l'influence des divers paramètres d'entrée (densité de courant, densité électronique, temps de montée du courant...) sur les fonctions de distribution. Pour cela, nous ajustons deux maxwelliennes qui correspondent au coeur de la distribution et à la population suprathermique. Nous mettons en avant le fait que le temps de montée du courant, c'est-à-dire le temps nécessaire pour atteindre la valeur maximale du courant, est un paramètre clef. En effet, augmenter ce temps influe essentiellement sur les températures : la température moyenne des électrons, mais aussi celle des électrons de la population représentant le coeur de la distribution et de la population suprathermique. La densité de courant joue également un rôle primordial.Augmenter la densité de courant augmente l'ensemble des paramètres : la densité et la vitesse moyenne des électrons runaway et les températures électroniques des deux populations. L'étude sur la densité a révélé que, plus la densité électronique totale augmente, plus la température et la vitesse moyenne des électrons suprathermiques diminuent.
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Повний текст джерелаtext