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Visar resultat 1 - 5 av 7 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. 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

  3. 2. GNSS hardware biases in code and carrier phase observables

    Författare :Martin Håkansson; Milan Horemuz; Anna B. O. Jensen; Lambert Wanninger; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; GNSS; GNSS positioning; hardware biases; phase biases; multi-GNSS; GPS; GLONASS; Galileo; BeiDou; satellite dependency; characterization; android; mass market; Group delay variations; nadir dependence; ionosphere modeling; ionospheric tomography; Geodesy and Geoinformatics; Geodesi och geoinformatik; Geodesi; Geodesy;

    Sammanfattning : GNSS hardware biases appear in code and phase observations, and originates both from the receiver and satellite hardware. The presence of biases in GNSS observations might affect the accuracy in precise GNSS positioning applications, and might also be of relevance in other GNSS applications. LÄS MER

  4. 3. Solar wind ions inside the induced magnetosphere of Mars

    Författare :Catherine Dieval; Christian Mazelle; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Rymdteknik; Space Technology;

    Sammanfattning : The subject of the thesis is analysis and modeling of the entry, transport, and atmospheric precipitation of solar wind ions, H+ and He2+, into the induced magnetosphere of Mars. The solar wind is a flow of charged particles emitted by the Sun. The solar wind carries with it a magnetic field, the interplanetary magnetic field (IMF). LÄS MER

  5. 4. The solar wind protons inside the induced magnetosphere of Mars

    Författare :Catherine Dieval; Maria Hamrin; Luleå tekniska universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Rymdteknik; Space Technology;

    Sammanfattning : Mars is an unmagnetized planet. Mars has no intrinsic magnetic field but has local magnetic anomalies in the crust. The solar wind, which is the plasma flowing from the Sun at supersonic speed, interacts with the magnetic fields of the currents induced in the conductive Martian ionosphere, deviates and slows down to subsonic speeds. LÄS MER

  7. 5. Multi-spectral analysis of fine scale aurora

    Författare :Hanna Dahlgren; Göran Marklund; Nickolay Ivchenko; Fred Sigernes; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Plasma physics; Plasmafysik; Optics; Optik;

    Sammanfattning : The Aurora Borealis is the visible manifestation of the complex plasma interaction between the solar wind and the Earth's magnetosphere and ionosphere. Ground based and in situ measurements demonstrate a prevalence of dynamic fine structure within auroral displays, with spatial scales down to tens of metres and time variations occurring on a fraction of a second. LÄS MER