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Visar resultat 1 - 5 av 105 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Numerical Simulation as a Tool for Studying Waves and Radiation in Space

   Författare :Lars Kristen Selberg Daldorff; Bo Thide; Francesco Califano; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; space physics; plasma physics; kinetic plasma; plasma simulations; beam instabilities; Space physics; Rymdfysik;

   Sammanfattning : Plasma physics governs the area of interactions between charged particles. As 99% of the visible universe is in a plasma state, it is an important topic in astronomy and space physics, where we already at an altitude of 60 km reach the plasma environment surrounding our planet in the form of the ionosphere. LÄS MER

3. 2. Plasma Arc Welding Simulation with OpenFOAM

   Författare :Margarita Sass-Tisovskaya; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : A simulation tool that is valid within the field of tandem arc welding(unsteady, three dimensional thermal plasma flow) has been developed,based on the open source CFD package OpenFOAM. The validation of the electromagnetic part of the solver has been done separately using a problem with a known solution. LÄS MER

4. 3. Theoretical Atomic Spectroscopy of Earthbound and Stellar Plasma

   Författare :Jon Grumer; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; atomstruktur; atomära processer; elektronkorrelation; plasmaspektroskopi; magnetfält; hyperfinstruktur; solkoronan; rymdväder; förekomst av grundämnen i stjärnor; datorsimuleringar; Zeemaneffekt; relativistiska effekter; atomic structure; atomic processes; computer simulation; electron correlation; relativistic atomic theory; plasma spectroscopy; Zeeman effect; magnetic fields; hyperfine structure; solar corona; space weather; stellar abundances; Fysicumarkivet A:2016:Grumer;

   Sammanfattning : Motivated by spectroscopic analysis of astrophysical and laboratory plasma, this thesis concerns the fundamental structure and spectral properties of atoms and their ions. The multiconfiguration Dirac-Hartree-Fock (MCDHF) method is used to predict the emission or absorption of radiation, by atomic systems in general, and of heavy and highly charged ions in particular. LÄS MER

5. 4. Numerical modeling of auroral processes

   Författare :Jörgen Vedin; Kjell Rönnmark; Robert Lysak; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; space plasma physics; auroral acceleration region; auroral current circuit; Alfvén waves; parallel electric fields; equation of state; fluid simulation; PIC simulation; Space physics; Rymdfysik;

   Sammanfattning : One 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. LÄS MER

7. 5. A Simulation Approach to High-Frequency Plasma Waves

   Författare :Etienne Koen; Tomas Karlsson; Orsolya Ferencz; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : Electrostatic waves in the form of Broadband Electrostatic Noise (BEN) have been observed in the Earth's auroral region associated with high geomagnetic activity. This broad frequency spectrum consists of three electrostatic modes, namely electron plasma, electron acoustic and beam-driven modes. LÄS MER