Sökning: "downward current region"

Visar resultat 1 - 5 av 8 avhandlingar innehållade orden downward current region.

  1. 1. Auroral Electric Fields From Satellite Observations and Numerical Modelling

    Författare :Tomas Karlsson; KTH; []
    Nyckelord :Satellite measurements; electric fields; ionosphere; magnetosphere; diverging electric fields; downward current region; black aurora; westward travelling surge; auroral bulge; subauroral ion drifts SAID ; subauroral electric fields SAEF ; mid-latit; TECHNOLOGY; TEKNIKVETENSKAP;

    Sammanfattning : This thesis is about electrodynamics of thehigh-latitude/auroral region of near-Earth space. The work ismainly based on electric field measurements made by the doubleprobe instrument on the Freja satellite at altitudes ofapproximately 800-1700 km, together with measurements fromother instruments on the same satellite, and ground-basedinstrumentation. LÄS MER

  3. 2. Cluster in situ studies of the auroral acceleration region

    Författare :Bin Li; Göran Marklund; Stein Haaland; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Cluster; Aurora acceleration region; Physics; Fysik;

    Sammanfattning : This thesis addresses a central topic in auroral physics, namely particle accelerationproducing intense aurora as well as energetic plasma outflow. Cluster satellitemeasurements of electric and magnetic fields, electrons and ions, collected across auroralfield lines, are used to study various aspects of the quasi-static auroral accelerationregion (AAR), its relation to the auroral density cavity, and the relative role of quasistaticand Alfvénic acceleration for producing aurora. LÄS MER

  4. 3. Multi-Spacecraft Observations of the Auroral Acceleration Region

    Författare :Soheil Sadeghi; Göran T. Marklund; Andris Vaivads; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : The two major agents for producing aurora are generally believed to be the quasi-static parallel electric fields, accelerating electrons in the auroral acceleration region (AAR), and Alfvén waves. The Cluster spacecraft quartet has made multi-spacecraft measurements in the AAR possible for the first time. LÄS MER

  5. 4. Investigations of auroral electric fields and currents

    Författare :Tommy Johansson; Göran Marklund; Kristina Lynch; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; auroral physics; auroral electric fields; auroral potential structures; auroral particle acceleration; Space physics; Rymdfysik;

    Sammanfattning : The Cluster spacecraft have been used to investigate auroral electric fields and field-aligned currents (FACs) at geocentric distances between 4 and 7 Re. The electric fields have been measured by the EFW instrument, consisting of two pairs of spherical probes, and the FACs have been calculated from measurements of the magnetic field by the FGM fluxgate magnetometer. LÄS MER

  7. 5. On mechanisms controlling air-sea gas exchange

    Författare :Lucía Gutiérrez-Loza; Anna Rutgersson; Erik Sahlée; Marcus B. Wallin; Tom Bell; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Air-sea gas exchange; eddy covariance; gas transfer velocity; Baltic Sea; Meteorologi; Meteorology;

    Sammanfattning : Carbon is essential to the Earth’s system functioning, playing a major role in physical and biogeochemical processes in the atmosphere, the terrestrial biosphere, and the oceans. The concentration of carbon-based greenhouse gases in the atmosphere, such as carbon dioxide (CO2) and methane (CH4), has been increasing since the industrial era. LÄS MER