Sökning: "Acoustic waves"

Visar resultat 11 - 15 av 124 avhandlingar innehållade orden Acoustic waves.

  1. 11. Electrostatic plasma waves associated with collisionless magnetic reconnection : Spacecraft observations

    Författare :Konrad Steinvall; Yuri Khotyaintsev; Daniel Graham; Andris Vaivads; Jonathan Rae; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Magnetic reconnection; Plasma waves; Electron holes; Solar wind; Magnetosphere; Magnetospheric Multiscale; Solar Orbiter; Fysik med inriktning mot rymd- och plasmafysik; Physics with specialization in Space and Plasma Physics;

    Sammanfattning : Magnetic reconnection is a fundamental plasma process where changes in magnetic field topology result in explosive energy conversion, plasma mixing, heating, and energization. In geospace, magnetic reconnection couples the Earth’s magnetosphere to the solar wind plasma, enabling plasma transport across the magnetopause. LÄS MER

  3. 12. Solitary waves and enhanced incoherent scatter ion lines

    Författare :Jonas Ekeberg; Lars Eliasson; Kristof Stasiewicz; Jan Trulsen; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; plasma waves and instabilities; nonlinear phenomena; solitons and solitary waves; ionosphere; Sun: corona; incoherent scatter radar; MHD; plasmavågor och instabiliteter; ickelinjära fenomen; solitoner och solitära vågor; jonosfär; solen: korona; inkoherent spridningsradar; MHD; Geocosmophysics and plasma physics; Geokosmofysik och plasmafysik; Space physics; Rymdfysik; Plasma physics; Plasmafysik; Non-linear dynamics; chaos; Icke-linjär dynamik; kaos; fysik; Physics; rymd- och plasmafysik; Space and Plasma Physics;

    Sammanfattning : This thesis addresses solitary waves and their significance for auroral particle acceleration, coronal heating and incoherent scatter radar spectra. Solitary waves are formed due to a balance of nonlinear and dispersive effects. LÄS MER

  4. 13. Cluster Observations and Theoretical Explanations of Broadband Waves in the Auroral Region

    Författare :Marie Backrud; Jan-Erik Wahlund; Mats André; David Knudsen; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Space and plasma physics; ion acoustic waves; auroral region; anomalous resistivity; Cluster; Rymd- och plasmafysik; Space physics; Rymdfysik;

    Sammanfattning : Broadband extremely low-frequency wave emissions below the ion plasma frequency have been observed by a number of spacecraft and rockets on auroral field lines. The importance of these broadband emissions for transverse ion heating and electron acceleration in the auroral regions is now reasonably well established. LÄS MER

  5. 14. Dispersion relations for extinction of acoustic and electromagnetic waves

    Författare :Christian Sohl; Institutionen för elektro- och informationsteknik; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

    Sammanfattning : This thesis deals with physical limitations on scattering and absorption of acoustic and electromagnetic waves. A general dispersion relation for the extinction cross section of such waves is derived from the holomorphic properties of the scattering amplitude in the forward direction. LÄS MER

  7. 15. Waves and instabilities in quantum plasmas

    Författare :Shahid Ali; Padma Kant Shukla; Mattias Marklund; Jose Tito Mendonca; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quantum mechanical effects; dusty plasma; linear and nonlinear waves; instabilities; nonlinear wave interactions; density gradients; magnetoplasmas.; Plasma physics; Plasmafysik;

    Sammanfattning : The study of waves and instabilities in quantum plasmas is of fundamental importance for understanding collective interactions in superdense astrophysical objects, in high intense laser-plasma/solid-matter interactions, in microelectronic devices and metallic nanostructures. In dense quantum plasmas, there are new pressure laws associated with the Fermi-Dirac distribution functions and new quantum forces associated with the quantum Bohm potential and the Bohr magnetization involving electron ½ spin. LÄS MER