Now showing items 1-20 of 30

  • Active region emission measure distributions and implications for nanoflare heating 

    Cargill, P.J. (2014-03-20) - Journal article
    The temperature dependence of the emission measure (EM) in the core of active regions coronal loops is an important diagnostic of heating processes. Observations indicate that EM(T) ~ T a below approximately 4 MK, with 2 < ...
  • 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 ...
  • A complex solar coronal jet with two phases 

    Chen, Jie; Su, Jiangtao; Deng, Yuanyong; Priest, E. R. (2017-05-04) - Journal article
    Jets often occur repeatedly from almost the same location. In this paper, a complex solar jet was observed with two phases to the west of NOAA AR 11513 on 2012 July 2. If it had been observed at only moderate resolution, ...
  • Coronal heating and nanoflares : current sheet formation and heating 

    Bowness, Ruth; Hood, Alan William; Parnell, Clare Elizabeth (2013-12) - Journal article
    Aims: Solar photospheric footpoint motions can produce strong, localised currents in the corona. A detailed understanding of the formation process and the resulting heating is important in modelling nanoflares, as a mechanism ...
  • Coronal heating by the partial relaxation of twisted loops 

    Bareford, Michael; Hood, Alan; Browning, Philippa (2013-02) - Journal article
    Context: Relaxation theory offers a straightforward method for estimating the energy that is released when a magnetic field becomes unstable, as a result of continual convective driving. Aims: We present new results obtained ...
  • Coronal heating in multiple magnetic threads 

    Tam, Kuan Vai; Hood, Alan William; Browning, Philippa; Cargill, Peter (2015-08) - Journal article
    Context. Heating the solar corona to several million degrees requires the conversion of magnetic energy into thermal energy. In this paper, we investigate whether an unstable magnetic thread within a coronal loop can ...
  • Current sheets in the solar corona : formation, fragmentation and heating 

    Bowness, Ruth (University of St Andrews, 2011-11-30) - Thesis
    In this thesis we investigate current sheets in the solar corona. The well known 1D model for the tearing mode instability is presented, before progressing to 2D where we introduce a non-uniform resistivity. The effect ...
  • The dependence of coronal loop heating on the characteristics of slow photospheric motions 

    Ritchie, M. L.; Wilmot-Smith, A. L.; Hornig, G. (2016-06-06) - Journal article
    The Parker hypothesis assumes that heating of coronal loops occurs due to reconnection, induced when photospheric motions braid field lines to the point of current sheet formation. In this contribution we address the ...
  • The detection of numerous magnetic separators in a three-dimensional magnetohydrodynamic model of solar emerging flux 

    Parnell, Clare Elizabeth; Maclean, Rhona Claire; Haynes, Andrew Lewis (2010-12-20) - Journal item
    Magnetic separators in three-dimensional (3D) magnetic fields are believed to be often associated with locations of magnetic reconnection. In this preliminary study, we investigate this relationship using data from a ...
  • Elongation of flare ribbons 

    Qiu, Jiong; Longcope, Dana W.; Cassak, Paul A.; Priest, Eric R. (2017-03-20) - Journal article
    We present an analysis of the apparent elongation motion of flare ribbons along the polarity inversion line (PIL), as well as the shear of flare loops in several two-ribbon flares. Flare ribbons and loops spread along the ...
  • 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 ...
  • Evolution of magnetic helicity during eruptive flares and coronal mass ejections 

    Priest, Eric Ronald; Longcope, D W; Janvier, M (2016-08) - Journal article
    During eruptive solar flares and coronal mass ejections, a non-potential magnetic arcade with much excess magnetic energy goes unstable and reconnects. It produces a twisted erupting flux rope and leaves behind a sheared ...
  • Flux-rope twist in eruptive flares and CMEs : due to zipper and main-phase reconnection 

    Priest, Eric Ronald; Longcope, D.W. (2017-01) - Journal article
    The nature of three-dimensional reconnection when a twisted flux tube erupts during an eruptive flare or coronal mass ejection is considered. The reconnection has two phases: first of all, 3D “zipper reconnection” propagates ...
  • Global sausage oscillation of solar flare loops detected by the Interface Region Imaging Spectrograph 

    Tian, Hui; Young, Peter R.; Reeves, Katharine K.; Wang, Tongjiang; Antolin, Patrick; Chen, Bin; He, Jiansen (2016-05-20) - Journal article
    An observation from the Interface Region Imaging Spectrograph reveals coherent oscillations in the loops of an M1.6 flare on 2015 March 12. Both the intensity and Doppler shift of Fe xxi 1354.08 Å show clear oscillations ...
  • Imaging observations of magnetic reconnection in a solar eruptive flare 

    Li, Y.; Sun, X.; Ding, M. D.; Qiu, J.; Priest, E. R. (2017-01-31) - Journal article
    Solar flares are among the most energetic events in the solar atmosphere. It is widely accepted that flares are powered by magnetic reconnection in the corona. An eruptive flare is usually accompanied by a coronal mass ...
  • The investigation of quasi-separatrix layers in solar magnetic fields 

    Restante, Anna Lisa (University of St Andrews, 2011-06-20) - Thesis
    The structure of the magnetic field is often an important factor in many energetic processes in the solar corona. To determine the topology of the magnetic field features such as null points, separatrix surfaces, and ...
  • Ionization in atmospheres of brown dwarfs and extrasolar planets. IV. The effect of cosmic rays 

    Rimmer, Paul; Helling, Christiane (2013-08-21) - Journal article
    Cosmic rays provide an important source for free electrons in Earth's atmosphere and also in dense interstellar regions where they produce a prevailing background ionization. We utilize a Monte Carlo cosmic ray transport ...
  • Magnetic skeletons and 3D magnetic reconnection 

    Haynes, Andrew L. (University of St Andrews, 2008-06-23) - Thesis
    The upper atmosphere of the sun, the solar corona, is approximately 1,000,000K hotter than the surface of the Sun, a property which cannot be explained by the normal processes of heat conduction and radiation. It is now ...
  • Magnetohydodynamics dynamical relaxation of coronal magnetic fields : II. 2D Magnetic X-Points 

    Fuentes-Fernández, Jorge; Parnell, Clare Elizabeth; Hood, Alan William (2011-12) - Journal article
    Context. Magnetic neutral points are potential locations for energy conversion in the solar corona. 2D X-points have been widely studied in the past, but only a few of those studies have taken finite plasma beta effects ...
  • 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. ...