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Title: Fast magnetoacoustic waves in non-equilibrium solar wind and coronal plasmas
Author: Selzer, Luke A.
ISNI:       0000 0004 5371 1674
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2015
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In this thesis the effect of collective particle behaviour within a plasma was explored using kinetic plasma theory in conjunction with magnetohydrodynamics (MHD). Collisionless or quasi-collisionless space plasmas were used as test laboratories in an attempt to understand the evolution of space plasmas. In a collisionless plasma, forces and fields are mediated through collective behaviour such as instabilities and plasma waves, thus the plasma parameters evolve due to modification by collective effects. In this work we implemented analytical and numerical techniques to predict the effect of collective behaviour. These hypotheses were then tested against experimental data as a validation process. The region near the Earth’s bow shock where incoming solar wind interacts with plasma emanating from the bow shock is known as the foreshock. This region is an abundant source of complex particle distributions with associated collective phenomena. We report the first observation of correlation between elevated solar wind core plasma temperatures and temperature anisotropy in the terrestrial foreshock. Direct comparison of contemporaneous anisotropic temperatures in the upstream solar wind and the foreshock suggests that the net heating of plasma is mediated via a increase of the parallel temperature in the foreshock region where ultra low frequency (ULF) plasma waves have been observed. We consider the possibility that a mechanism based on Landau damping, where solar wind plasma temperature parallel to the background magnetic field is increased by interaction with oblique compressible fast magneto-acoustic ULF waves, influences temperature anisotropy. Next the impact of wave phenomena on the radio emission fine structure in flaring loops of the solar corona was investigated. In particular, the impact of MHD oscillations on zebra pattern (ZP) radio emission. Initially static analytical studies were carried in one and two dimensions to show it was possible do derive a ZP using MHD techniques. The dynamics of ZP formation in the presence of MHD oscillations were then analytically studied to show the presence of ‘wiggles’ in the ZP. These results were then repeated using numerical simulations using the Lare2D MHD code. The catalogue of results suggests that the detected ZP wiggles were caused by a standing sausage oscillation. We affirm this conclusion using the observation that both instant frequencies of individual stripes and their spectral separation oscillate with the same periods. Thus it is consistent with a sausage oscillation that perturb both the plasma density and magnetic field. These results are further underpinned by comparison to experimentally obtained ZP wiggles which exhibit similar periodicities. This new result could lead to a method for the direct measurement of coronal magnetic fields in flaring loops.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics