Now showing items 1-20 of 31

    • Aspects of three-dimensional MHD : magnetic reconnection and rotating coronae 

      Al-Salti, Nasser S. (University of St Andrews, 2010-06-23) - Thesis
      Solutions of the magnetohydrodynamic (MHD) equations are very important for modelling laboratory, space and astrophysical plasmas, for example the solar and stellar coronae, as well as for modelling many of the dynamic ...
    • Can substorm particle acceleration be applied to solar flares? 

      Birn, Joachim; Battaglia, Marina; Fletcher, Lyndsay; Hesse, Michael; Neukirch, Thomas (2017-10-20) - Journal article
      Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard ...
    • Collisionless current sheet equilibria 

      Neukirch, Thomas; Wilson, Fiona; Allanson, Oliver Douglas (2018-01) - Journal article
      Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic ...
    • A combined theory for magnetohydrodynamic equilibria with anisotropic pressure and magnetic shear 

      Hodgson, Jonathan David Brockie; Neukirch, Thomas (2017-03-10) - Journal article
      We present a new approach to the theory of magnetohydrodynamic equilibria with anisotropic pressure, magnetic shear and translational/rotational invariance. This approach involves combining two existing formalisms in order ...
    • A detailed investigation of the properties of a Vlasov-Maxwell equilibrium for the force-free Harris sheet 

      Neukirch, Thomas; Wilson, F.; Harrison, M. G. (2009-12) - Journal article
      A detailed discussion is presented of the Vlasov-Maxwell equilibrium for the force-free Harris sheet recently found by Harrison and Neukirch [Phys. Rev. Lett. 102, 135003 (2009)]. The derivation of the distribution function ...
    • Elements of solar activity : particle acceleration and filament formation 

      Wood, Paul D. (University of St Andrews, 2005-01) - Thesis
      This thesis studies the acceleration of particles to super-thermal energies in explosive solar events as well as the magnetic changes in connectivity that may be responsible for changes in the morphology of quiescent ...
    • Equilibrium and dynamics of collisionless current sheets 

      Harrison, Michael George (University of St Andrews, 2009-06-24) - Thesis
      In this thesis examples of translationally invariant one-dimensional (1D) Vlasov-Maxwell (VM) equilibria are investigated. The 1D VM equilibrium equations are equivalent to the motion of a pseudoparticle in a conservative ...
    • Equilibrium and stability properties of collisionless current sheet models 

      Wilson, Fiona (University of St Andrews, 2013-06-28) - Thesis
      The work in this thesis focuses primarily on equilibrium and stability properties of collisionless current sheet models, in particular of the force-free Harris sheet model. A detailed investigation is carried out into ...
    • An exact collisionless equilibrium for the Force-Free Harris Sheet with low plasma beta 

      Allanson, Oliver Douglas; Neukirch, Thomas; Wilson, Fiona; Troscheit, Sascha (2015-10) - Journal article
      We present a first discussion and analysis of the physical properties of a new exact collisionless equilibrium for a one-dimensional nonlinear force-free magnetic field, namely, the force-free Harris sheet. The solution ...
    • Force-free collisionless current sheet models with non-uniform temperature and density profiles 

      Wilson, Fiona; Neukirch, Thomas; Allanson, Oliver Douglas (2017-08-17) - Journal article
      We present a class of one-dimensional, strictly neutral, Vlasov-Maxwell equilibrium distribution functions for force-free current sheets, with magnetic fields defined in terms of Jacobian elliptic functions, extending the ...
    • From one-dimensional fields to Vlasov equilibria : Theory and application of Hermite Polynomials 

      Allanson, Oliver Douglas; Neukirch, Thomas; Troscheit, Sascha; Wilson, Fiona (2016-06) - Journal article
      We consider the theory and application of a solution method for the inverse problem in collisionless equilibria, namely that of calculating a Vlasov-Maxwell equilibrium for a given macroscopic (fluid) equilibrium. Using ...
    • An investigation of rotating magnetospheres 

      Ryan, Richard Daniel (University of St Andrews, 2002-11) - Thesis
      In this thesis we will construct simple models of rotating stellar and planetary magnetospheres within the framework of ideal MHD. These models will take the basic outline of a stellar magnetosphere that we have outlined ...
    • Investigations of current build up in topologically simple magnetic fields 

      Bocquet, Francois-Xavier (University of St Andrews, 2005-06) - Thesis
      The solar corona is a highly conductive plasma which is dominated by the coronal magnetic field. Observations show that important solar phenomena like flares or the heating of the corona are driven by magnetic energy, ...
    • Loss cone evolution and particle escape in collapsing magnetic trap models in solar flares 

      Eradat Oskoui, Solmaz; Neukirch, Thomas; Grady, Keith James (2014-03) - Journal article
      Context. Collapsing magnetic traps (CMTs) have been suggested as one possible mechanism responsible for the acceleration of high-energy particles during solar flares. An important question regarding the CMT acceleration ...
    • Magneto-static modeling from SUNRISE/IMaX : application to an active region observed with SUNRISE II 

      Wiegelmann, T.; Neukirch, Thomas; Nickeler, D. H.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; Noort, M. van; Rodríguez, J. Blanco; Del Toro Iniesta, J. C.; Suárez, D. Orozco; Schmidt, W.; Pillet, V. Martínez; Knölker, M. (2017-03-22) - Journal article
      Magneto-static models may overcome some of the issues facing force-free magnetic field extrapolations. So far they have seen limited use and have faced problems when applied to quiet-Sun data. Here we present a first ...
    • Magneto-static modeling of the mixed plasma Beta solar atmosphere based on SUNRISE/IMaX data 

      Wiegelmann, Thomas; Neukirch, Thomas; Nickeler, Dieter; Solanki, Sami; Martinez Pillet, Valentin; Borrero, Juan Manule (2015-12) - Journal article
      Our aim is to model the 3D magnetic field structure of the upper solar atmosphere, including regions of non-negligible plasma beta. We use high-resolution photospheric magnetic field measurements from SUNRISE/IMaX as ...
    • Magnetohydrostatic modelling of stellar coronae 

      MacTaggart, David; Gregory, Scott; Neukirch, Thomas; Donati, Jean-Francois (2016-02-11) - Journal article
      We introduce to the stellar physics community a method of modelling stellar coronae that can be considered to be an extension of the potential field. In this approach, the magnetic field is coupled to the background ...
    • Neutral and non-neutral collisionless plasma equilibria for twisted flux tubes : the Gold-Hoyle model in a background field 

      Allanson, Oliver Douglas; Wilson, Fiona; Neukirch, Thomas (2016-09) - Journal article
      We calculate exact one-dimensional collisionless plasma equilibria for a continuum of flux tube models, for which the total magnetic field is made up of the `force-free' Gold-Hoyle magnetic flux tube embedded in a uniform ...
    • New aspects of particle acceleration in collapsing magnetic traps 

      Eradat Oskoui, Solmaz (University of St Andrews, 2014-01) - Thesis
      Collapsing magnetic traps (CMTs) have been suggested as one of the mechanisms that could contribute to particle energisation in solar flares. The basic idea behind CMTs is that charged particles will be trapped on the ...
    • On the application of numerical continuation methods to two- and three-dimensional solar and astrophysical problems 

      Romeou, Zaharenia (University of St Andrews, 2002-06) - Thesis
      In this thesis, applications of a numerical continuation method to two- and three-dimensional bifurcation problems are presented. The 2D problems are motivated by solar applications. In particular, it is shown that the ...