Sökning: "auroral acceleration region"

Visar resultat 1 - 5 av 12 avhandlingar innehållade orden auroral acceleration region.

1. 1. 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

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. 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

5. 4. The importance of waves in space plasmas : Examples from the auroral region and the magnetopause

   Författare :Gabriella Stenberg; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Space and plasma physics; Plasma waves; magnetospheric physics; magnetopause; auroral region; wave distribution function; space exploration; reconnection; current tubes; Rymd- och plasmafysik; Space physics; Rymdfysik; rymdfysik; Space Physics;

   Sammanfattning : This thesis discusses the reasons for space exploration and space science. Space plasma physics is identified as an essential building block to understand the space environment and it is argued that observation and analysis of space plasma waves is an important approach.Space plasma waves are the main actors in many important processes. LÄS MER

7. 5. Satellite observations of auroral acceleration processes

   Författare :Lars Eliasson; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Aurora; particle acceleration; space plasma; magnetosphere; ionosphere; polar cap; satellite observations;

   Sammanfattning : Measurements with satellite and sounding rocket borne instruments contain important information on remote and local processes in regions containing matter in the plasma state. The characteristic features of the particle distributions can be used to explain the morphology and dynamics of the different plasma populations. LÄS MER