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Electromagnetic interaction of localized upper hybrid oscillations in a system of density depletions
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
2006 (English)In: Advances in Space Research, ISSN 0273-1177, Vol. 38, no 11, 2516-2517 p.Article in journal (Refereed) Published
Abstract [en]

We present the results of the investigation of interaction of different depletions of plasma density by Z-mode radiation. It is shown that more profitable disposition of cavities in space is random. The amplitude of the radiated Z-mode in this case is of the order of the amplitude of the pumping ordinary wave, but the amplitude of trapped into cavities upper hybrid wave is maximum and can be significantly higher than the amplitude of the pumping wave.

Place, publisher, year, edition, pages
2006. Vol. 38, no 11, 2516-2517 p.
Keyword [en]
electromagnetic waves, ionospheric disturbances and modifications
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-91833DOI: 10.1016/j.asr.2005.02.039ISI: 000202988800034OAI: oai:DiVA.org:uu-91833DiVA: diva2:164691
Available from: 2004-05-12 Created: 2004-05-12 Last updated: 2011-05-04Bibliographically approved
In thesis
1. Interaction between Electromagnetic Waves and Localized Plasma Oscillations
Open this publication in new window or tab >>Interaction between Electromagnetic Waves and Localized Plasma Oscillations
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Växelverkan mellan elektromagnetiska vågor och lokaliserade plasmaoscillationer
Abstract [en]

This thesis treats interaction between electromagnetic waves and localized plasma oscillations. Two specific physical systems are considered, namely artificially excited magnetic field-aligned irregularities (striations) and naturally excited lower hybrid solitary structures (LHSS). Striations are mainly density depletions of a few percent that are observed when a powerful electromagnetic wave, a pump wave, is launched into the ionosphere. The striations are formed by upper hybrid (UH) oscillations that are localized in the depletion where they are generated by the linear conversion of the pump field on the density gradients. However, the localization is not complete as the UH oscillation can convert to a propagating electromagnetic Z mode wave. This process, termed Z mode leakage, causes damping of the localized UH oscillation. The Z mode leakage is investigated and the theory predicts non-Lorentzian skewed shapes of the resonances for the emitted Z mode radiation. Further, the interaction between individual striations facilitated by the Z mode leakage is investigated. The LHSS are observed by spacecraft in the ionosphere and magnetosphere as localized waves in the lower hybrid (LH) frequency range that coincides with density cavities. The localized waves are immersed in non-localized wave activity. The excitation of localized waves with frequencies below LH frequency is modelled by scattering of electromagnetic magnetosonic (MS) waves off a preexisting density cavity. It is shown analytically that an incident MS wave with frequency less than the minimum LH frequency inside the cavity is focused to localized waves with left-handed rotating wave front. In addition, the theory is shown to be consistent with observations by the Freja satellite. For frequencies between the minimum LH frequency inside the cavity and the ambient LH frequency, the MS wave is instead mode converted and excites pressure driven LH oscillations. This process is studied in a simplified geometry.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 43 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 985
Keyword
Space and plasma physics, space physics, plasma physics, radio waves, ionospheric modification, density depleations, field-aligned irregularities, lower hybrid solitary structures, lower hybrid cavities, Z mode waves, magnetosonic waves, scattering, mode conversion, Rymd- och plasmafysik
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-4282 (URN)91-554-5982-X (ISBN)
Public defence
2004-06-03, Häggsalen (Room 10132), Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 13:15
Opponent
Supervisors
Available from: 2004-05-12 Created: 2004-05-12Bibliographically approved

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