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Nonlinear waves, structure form ation and particle acceleration by waves in space physics

Başlık çevirisi mevcut değil.

  1. Tez No: 402680
  2. Yazar: DEFNE ÜÇER ŞAYLAN
  3. Danışmanlar: PROF. VITALI D. SHAPIRO, PROF. KEVIN B. QUEST
  4. Tez Türü: Doktora
  5. Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2004
  8. Dil: İngilizce
  9. Üniversite: University of California San Diego
  10. Enstitü: Yurtdışı Enstitü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 126

Özet

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Özet (Çeviri)

The first p art of this dissertation is devoted to the theory of nonlinear m odulational interaction of lower-hybrid waves w ith slow background density fluctuations such as ion-acoustic mode and inertial Alfven mode. This type of interaction leads to m odulational instability and localization of lower hybrid waves in the plane perpendicular to the magnetic field. The field localizations are correlated with depletions or humps in local plasm a density. Density cavities filled with field fluctuations w ith frequency of the order of local lower-hybrid frequency are commonly observed in auroral ionosphere of the E arth. These structures are named lower-hybrid solitary structures. In this dissertation, the theory of m odulational interaction of lower-hybrid waves with ion-acoustic waves and inertial Alfven waves is studied in the context of auroral ionosphere. The behavior of lower-hybrid waves are investigated in the pre-determined cylindrical background density profile. It is found th a t the lower-hybrid waves are trapped in density depletions as well as density humps. The wave trajectories show that the wave is best confined in the regions of maximum density gradient. Then the Reynolds' stresses of the lower-hybrid waves are added to the governing equations describing the interaction. The conditions for occurrence of the moduxlational instability are analyzed. The evolution equations for the envelope lowerhybrid am plitude is obtained for the case when the interacting mode is ion-acoustic as well as inertial Alfven. It is found th a t the w idth of an initial modulation in the lower-hybrid wave am plitude contracts by the evolution of modulational instability. This leads to“collapse”, or a finite-time blow-up solution. In th e second part of the dissertation,“shock surfing acceleration”is considered as a possible candidate for ion acceleration at quasi-perpendicular coliisionless astrophysieal shock waves in plasma. The modification of the acceleration mechanism for relativistic regime is analyzed. It is shown th a t one of the lim itations to shock surfing acceleration ceases at relativistic energies. For sufficiently steep shock fronts, the transition to“relativistic regime”results with acceleration up to ultra-relativistic energies at time scales much shorter th an tim e scales predicted by the widely accepted acceleration mechanism, diffusive shock acceleration. The critical energy for the transition to the relativistic regime is estim ated, and conditions for achieving this critical energy are discussed.

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