Now showing items 1-20 of 108

    • Boundary layer flow beneath an internal solitary wave of elevation 

      Carr, Magda; Davies, P A (2010-02) - Journal article
      The wave-induced flow over a fixed bottom boundary beneath an internal solitary wave of elevation propagating in an unsheared, two-layer, stably stratified fluid is investigated experimentally. Measurements of the velocity ...
    • Energy dissipation and resolution of steep gradients in one-dimensional Burgers flows 

      Tran, Chuong Van; Dritschel, David Gerard (2010-03) - Journal article
      Traveling-wave solutions of the inviscid Burgers equation having smooth initial wave profiles of suitable shapes are known to develop shocks (infinite gradients) in finite times. Such singular solutions are characterized ...
    • Solar cycle variation of magnetic flux ropes in a quasi-static coronal evolution model 

      Yeates, A. R.; Constable, J. A.; Martens, P. C. H. (2010-05) - Journal article
      The structure of electric current and magnetic helicity in the solar corona is closely linked to solar activity over the 11-year cycle, yet is poorly understood. As an alternative to traditional current-free "potential ...
    • Effects of thermal conduction and compressive viscosity on the period ratio of the slow mode 

      Macnamara, Cicely Krystyna; Roberts, Bernard (2010-06) - Journal article
      Aims: Increasing observational evidence of wave modes brings us to a closer understanding of the solar corona. Coronal seismology allows us to combine wave observations and theory to determine otherwise unknown parameters. ...
    • Shallow-water vortex equilibria and their stability 

      Płotka, H.; Dritschel, D.G. (2011-01-01) - Journal article
      We first describe the equilibrium form and stability of steadily-rotating simply-connected vortex patches in the single-layer quasi-geostrophic model of geophysical fluid dynamics. This model, valid for rotating shallow-water ...
    • Instability in internal solitary waves with trapped cores 

      Carr, Magda; King, Stuart Edward; Dritschel, David Gerard (2012-01) - Journal article
      A numerical method that employs a combination of contour advection and pseudo-spectral techniques is used to investigate instability in internal solitary waves with trapped cores. A three-layer configuration for the ...
    • Magnetohydrodynamics dynamical relaxation of coronal magnetic fields : III. 3D spiral nulls 

      Fuentes-Fernandez, Jorge; Parnell, Clare E. (2012-06) - Journal article
      Context: The majority of studies on stressed 3D magnetic null points consider magnetic reconnection driven by an external perturbation, but the formation of a genuine current sheet equilibrium remains poorly understood. ...
    • Nonlinear wave propagation and reconnection at magnetic X-points in the Hall MHD regime 

      Threlfall, James William; Parnell, Clare Elizabeth; De Moortel, Ineke; McClements, Ken; Arber, Tony D. (2012-07) - Journal article
      Context: The highly dynamical, complex nature of the solar atmosphere naturally implies the presence of waves in a topologically varied magnetic environment. Here, the interaction of waves with topological features such ...
    • On energetics and inertial-range scaling laws of two-dimensional magnetohydrodynamic turbulence 

      Blackbourn, Luke Austen Kazimierz; Tran, Chuong Van (2012-07) - Journal article
      We study two-dimensional magnetohydrodynamic turbulence, with an emphasis on its energetics and inertial range scaling laws. A detailed spectral analysis shows that dynamo triads (those converting kinetic into magnetic ...
    • Two-dimensional magnetohydrodynamic turbulence in the small magnetic Prandtl number limit 

      Dritschel, David Gerard; Tobias, Steve (2012-07-01) - Journal article
      In this paper we introduce a new method for computations of two-dimensional magnetohydrodynamic (MHD) turbulence at low magnetic Prandtl number $\Pra=\nu/\eta$. When $\Pra \ll 1$, the magnetic field dissipates at a scale ...
    • Study of the three-dimensional shape and dynamics of coronal loops observed by Hinode/EIS 

      Syntelis, P.; Gontikakis, C.; Georgoulis, M. K.; Alissandrakis, C. E.; Tsinganos, K. (2012-10) - Journal article
      We study plasma flows along selected coronal loops in NOAA Active Region 10926, observed on 3 December 2006 with Hinode’sEUVImaging Spectrograph (EIS). From the shape of the loops traced on intensity images and the Doppler ...
    • Laboratory astrophysics : investigation of planetary and astrophysical maser emission 

      Speirs, David; Cairns, R Alan; Kellett, Barry; Vorgul, Irena; McConville, Sandra; Cross, Adrian; Phelps, Alan; Ronald, Kevin; Bingham, Robert (2013) - Journal article
      This paper describes a model for cyclotron maser emission applicable to planetary auroral radio emission, the stars UV Ceti and CU Virginus, blazar jets and astrophysical shocks. These emissions may be attributed to energetic ...
    • Vortical control of forced two-dimensional turbulence 

      Fontane, Jerome Jacob Louis; Dritschel, David Gerard; Scott, Richard Kirkness (2013-01-14) - Journal article
      A new numerical technique for the simulation of forced two-dimensional turbulence[D. Dritschel and J. Fontane, “The combined Lagrangian advection method,” J. Comput. Phys.229, 5408–5417 (Year: 2010)10.1016/j.jcp.2010.03.048] ...
    • Ultraviolet and extreme-ultraviolet emissions at the flare footpoints observed by atmosphere imaging assembly 

      Qiu, J.; Sturrock, Z.; Longcope, D.W.; Klimchuk, J.A.; Liu, W.-J. (2013-09-01) - Journal article
      A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a two-phase evolution pattern of UV 1600 Å emission at the feet of these ...
    • Magnetohydrodynamics dynamical relaxation of coronal magnetic fields : IV. 3D tilted nulls 

      Fuentes-Fernandez, Jorge; Parnell, Clare E. (2013-09-12) - Journal article
      In this paper we study current accumulations in 3D "tilted" nulls formed by a folding of the spine and fan. A non-zero component of current parallel to the fan is required such that the null's fan plane and spine are not ...
    • Resistive magnetohydrodynamic reconnection : resolving long-term, chaotic dynamics 

      Keppens, R.; Porth, O.; Galsgaard, K.; Frederiksen, J.T.; Restante, A.L.; Lapenta, G.; Parnell, C. (2013-09-13) - Journal article
      In this paper, we address the long-term evolution of an idealised double current system entering reconnection regimes where chaotic behavior plays a prominent role. Our aim is to quantify the energetics in high magnetic ...
    • The effect of slip length on vortex rebound from a rigid boundary 

      Sutherland, D.; Macaskill, C.; Dritschel, D.G. (2013-09-23) - Journal article
      The problem of a dipole incident normally on a rigid boundary, for moderate to large Reynolds numbers, has recently been treated numerically using a volume penalisation method by Nguyen van yen, Farge, and Schneider [Phys. ...
    • Potential Evidence for the Onset of Alfvénic Turbulence in Trans-equatorial Coronal Loops 

      De Moortel, Ineke; McIntosh, Scott; Threlfall, James William; Bethge, Christian; Liu, J (2014-02-10) - Journal article
      This study investigates Coronal Multi-channel Polarimeter Doppler-shift observations of a large, off-limb, trans-equatorial loop system observed on 2012 April 10-11. Doppler-shift oscillations with a broad range of frequencies ...
    • 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 ...
    • Simply-connected vortex-patch shallow-water quasi-equilibria 

      Plotka, Hanna; Dritschel, David Gerard (2014-03-05) - Journal article
      We examine the form, properties, stability and evolution of simply-connected vortex-patch relative quasi-equilibria in the single-layer ƒ-plane shallow-water model of geophysical fluid dynamics. We examine the effects of ...