Spatio-temporal structure of a poloidal Alfven wave detected by Cluster adjacent to the dayside plasmapause
2008 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 7, 1805-1817 p.Article in journal (Refereed) Published
A case study of a poloidal ULF pulsation near the dayside plasmapause is presented based on Cluster observations of magnetic and electric fields. The pulsation is detected close to the magnetic equatorial plane at L shells L=[4.4, 4.6] and oscillates with a frequency of f=23 mHz. Investigating the wave energy flux reveals the standing wave nature of the observed pulsation. An estimation of the azimuthal wave number exposes a narrow azimuthal structure of the wave field with m approximate to 160. Spatial and temporal characteristics of the pulsation are analyzed in detail by representing data in a field line related coordinate system and a range-time-intensity representation. This allows an estimation of both the spatial extension of the wave field in the radial direction and its temporal decay rate. The analysis furthermore indicates that the same field lines are excited to a standing wave oscillation twice. Furthermore an accurate identification of a phase jump of the wave field across L shells is possible. Comparing the radial localization of the detected wave with theoretically expected field line eigenfrequencies reveals that the wave field is confined in the Alfven resonator at the outer edge of the plasmapause.
Place, publisher, year, edition, pages
2008. Vol. 26, no 7, 1805-1817 p.
magnetospheric physics, magnetosphere-ionosphere interactions, MHD, waves and instabilities, plasmasphere, field line resonances, oblique magnetic-fields, geomagnetic-pulsations, hydromagnetic-waves, ulf pulsations, axisymmetrical magnetosphere, earths magnetosphere, ballooning modes, electric-field, ionosphere
Geophysics Fusion, Plasma and Space Physics
IdentifiersURN: urn:nbn:se:kth:diva-17738ISI: 000258074300013ScopusID: 2-s2.0-46449086376OAI: oai:DiVA.org:kth-17738DiVA: diva2:335783
QC 201410212010-08-052010-08-052014-10-21Bibliographically approved