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Multi-spacecraft determination of wave characteristics near the proton gyrofrequency in high-altitude cusp
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för astronomi och rymdfysik.
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2005 Ingår i: Annales Geophysicae, Vol. 23, s. 983-995Artikel i tidskrift (Refereegranskat) Published
Ort, förlag, år, upplaga, sidor
2005. Vol. 23, s. 983-995
Identifikatorer
URN: urn:nbn:se:uu:diva-93682OAI: oai:DiVA.org:uu-93682DiVA, id: diva2:167232
Tillgänglig från: 2005-11-03 Skapad: 2005-11-03 Senast uppdaterad: 2014-11-12Bibliografiskt granskad
Ingår i avhandling
1. Space Plasma Dynamics: Instabilities, Coherent Vortices and Covariant Parametrization
Öppna denna publikation i ny flik eller fönster >>Space Plasma Dynamics: Instabilities, Coherent Vortices and Covariant Parametrization
2005 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The magnetospheric cusps are two funnel-like regions of Earth's magnetosphere where solar wind plasma can have direct access to the ionosphere. The cusps are very dynamic regions where wave-particle interactions continuously take place and redistribute energy among different particle populations. In this thesis, both low and high frequency plasma waves in the cusp have been studied in detail using data from the Cluster spacecraft mission. The waves were studied with respect to frequency, Poynting flux and polarization. Wavelengths have also been estimated using multi-spacecraft techniques. At low frequencies, kinetic Alfvén waves and nonpotential ion cyclotron waves are identified and at high frequencies, electron cyclotron waves, whistler waves, upper-hybrid and RX-waves are observed. A common generation mechanism called the shell-instability is proposed for several of the wave modes present in the cusp, both at low and high frequencies.

The plasma in the cusp is shown to be strongly inhomogeneous. In an inhomogeneous low-frequency magnetoplasma, kinetic Alfvén waves couple to drift-waves. Such drift-kinetic Alfvén waves have long been believed to nonlinearly self-interact and form coherent structures in the form of drift-kinetic Alfvén vortices. In this thesis the first unambiguous direct measurements confirming the existence of such vortices in a turbulent space plasma are presented. Some of the crucial parameters such as the vortex radius are determined.

Plasma theory is electrodynamics applied to a large collection of charged particles. In this thesis a new way of looking at the fundamental Maxwell tensor is presented. A covariant spectral density tensor containing information on electromagnetic waves is formed. This tensor is then decomposed into irreducible components by using the spinor formalism for an arbitrary metric. The obtained fundamental tensors are shown to correspond both to well known tensors in Maxwell's theory, as well as several physically interesting new tensors.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2005. s. vii + 57
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 113
Nyckelord
Space and plasma physics, space physics, plasma, instabilities, turbulence, coherent structures, vortex, self-organization, magnetosphere, waves, electromagnetism, covariant, space instrumentation, Rymd- och plasmafysik
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:uu:diva-6051 (URN)91-554-6386-X (ISBN)
Disputation
2005-11-25, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:00
Opponent
Handledare
Tillgänglig från: 2005-11-03 Skapad: 2005-11-03Bibliografiskt granskad

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Vaivads, Andris

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