Sökning: "Spectral lines"

Visar resultat 16 - 20 av 121 avhandlingar innehållade orden Spectral lines.

1. 16. 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

3. 17. Fine-scale morphology and spectral characteristics of active aurora

   Författare :Hanna Dahlgren; Göran Marklund; Nickolay Ivchenko; Kari Kaila; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Aurora; Space physics; Rymdfysik;

   Sammanfattning : Ground-based and in-situ observations of the aurora demonstrate an extreme richness in fine structure, with spatial scales down to tens of metres and time variations occurring on a fraction of a second. To further our understanding of the aurora, it is esssential to understand the mechanisms responsible for the small-scale structuring, since this is an intrinsic property of the auroral plasma. LÄS MER

4. 18. Towards detecting lines from dark matter annihilations with GLAST

   Författare :Tomi Ylinen; Mark Pearce; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Physics; Fysik;

   Sammanfattning : Dark matter (DM) constitutes one of the most intriguing but so far unresolved issues in physics. In many extensions of the Standard Model of particle physics, the existence of a stable Weakly Interacting Massive Particle (WIMP) is predicted. LÄS MER

5. 19. An Observational Study of Accretion Processes in T Tauri Stars

   Författare :Henricus Cornelis Stempels; Nikolai Piskunov; Gibor Basri; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Star formation; T Tauri stars; Emission lines; Accretion; NLTE radiative transfer; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Astronomy; Astronomi;

   Sammanfattning : This thesis is a detailed observational study of the accretion processes in T Tauri stars (TTS). The interaction between the central star, the circumstellar disk and the magnetic field gives rise to a wide range of features in the spectra of TTS. LÄS MER

7. 20. High Spectral Efficiency Fiber-Optic Transmission Systems Using Pilot Tones

   Författare :Mikael Mazur; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Coherent Optical Communications; Analog Optical Signal Processing;

   Sammanfattning : Modern fiber-optic communication systems combine state-of-the-art components with powerful digital signal processing (DSP) to maximize the system spectral efficiency (SE). Systems rely on wavelength-division multiplexing, including superchannel transmission, to enable transmission over the available bandwidth which reaches about 10 THz when accounting for the so-called C and L bands. LÄS MER