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Title: Plasma heating and kinetic instabilities in the terrestrial foreshock
Author: O'Connell, Daniel J.
ISNI:       0000 0004 7425 6092
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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The terrestrial foreshock, the area upstream of, and magnetically connected to, the bow shock is a complex system in which the turbulent, supersonic and superalfvénic solar wind encounters the Earth’s magnetosphere. As a result, particle populations stream sunwards against the solar wind flow, creating a kinetic two-stream instability that leads to a variety of linear and nonlinear plasma processes. Foreshock plasma is collisionless, and the instability supports a variety of ultra-low frequency (ULF) modes. A statistical technique, based on categorizing wavenumber-frequency pairs by their associated power, is used to determine the dispersion relations for ULF modes in a number of case studies using magnetic field data from two-point measurements of the Cluster mission. Sunward-propagating fast magnetosonic and beam resonant modes are identified, as well as Alfvén modes propagating both sunwards and anti-sunwards. The fast magnetosonic modes are advected towards the Earth by the solar wind, and due to a cubic nonlinearity, steepen into sharply peaked waves. Three examples of these nonlinear wavetrains are compared to solutions of the derivative nonlinear Schrödinger equation, and are found to be in good agreement. The impact of the waves on the form of the pseudopotential, a quantity related to core plasma parameters, is also discussed. Wave-wave interactions are investigated for a case study of Cluster data, with a focus on energy transfer between ULF modes and a band of frequencies centred at 1Hz. Evidence for three-wave processes, formed by quadratic nonlinearities that interact between triads of frequencies that satisfy the frequency (f1 + f2 + f3) and wavenumber (k1 + k2 + k3) resonance conditions, is presented. Evidence for four wave processes in the same interval is also discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics