Sökning: "NATURVETENSKAP Fysik Astronomi och astrofysik"

Visar resultat 16 - 20 av 468 avhandlingar innehållade orden NATURVETENSKAP Fysik Astronomi och astrofysik.

  1. 16. Drift and Mirror Modes in Magnetized Plasmas

    Författare :Ingmar Sandberg; Padma Shukla; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; tokamak plasma; drift waves; space plasma; mirror instability.; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Space and Plasma Physics; rymd- och plasmafysik;

    Sammanfattning : Low frequency plasma instabilities driven by plasma inhomogeneity and velocity anisotropies are major candidates for the explanation of various phenomena observed in fusion and space plasmas. For low-β fusion plasma, the influence of plasma rotation and finite ion temperature on the structure and the type of toroidal drift eigenmodes in tokamaks is investigated rigorously, including the effects induced by the toroidal geometry such as the coupling mode, the radial variation of plasma rotation velocity and the magnetic shear. LÄS MER

  3. 17. Advancement of THz integrated SIS mixers for radio astronomy

    Författare :Raquel Monje; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

    Sammanfattning : .... LÄS MER

  4. 18. The faintest stars : A study of white, red and brown dwarfs

    Författare :Leif Festin; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; brown dwarfs; white dwarfs; M dwarf; low luminosity; luminosity function; mass function; Pleiades; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; astronomi; Astronomy;

    Sammanfattning : The local space density of the faintest stars, including M dwarfs, white dwarfs and brown dwarfs has been studied by two different methods.By using dark nebulae as opaque outer screens, the luminosity functions of M dwarfs and white dwarfs were studied as volume-limited and dynamically unbiassed foreground samples. LÄS MER

  5. 19. Gas Production in Distant Comets

    Författare :Marcus Gunnarsson; F Peter Schloerb; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Comets; Radio Astronomy; Molecular Spectroscopy; Coma Models; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; astronomi; Astronomy;

    Sammanfattning : Molecular spectroscopy at radio wavelengths is a tool well suited for studying the composition and outgassing kinematics of cometary comae. This is particularly true for distant comets, i.e. comets at heliocentric distances greater than a few AU, where the excitation of molecules is inefficient other than for rotational energy levels. LÄS MER

  7. 20. A study of possible chemical inhomogeneities of dwarf irregular galaxies and the influence on the Z-L relationship

    Författare :Ana Maria Hidalgo-Gámez; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; dwarf irregular galaxies; chemical abundances; metallicity-luminosity relationship; individual galaxies: NGC 6822; IC 4662; IC 10; ESO 245-G05; NGC 1569; IC 5152; DDO 53 and DDO 190; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; astronomi; Astronomy;

    Sammanfattning : A study on the chemical abundances of dwarf irregular galaxies (dI's) is presented in this work. This type of galaxies have typically low metallicity. First of all, a definition of dI is proposed, in order to obtain a homogeneous group of targets. LÄS MER