Critical conditions for magnetic instabilities in force-free coronal loops

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Ideal MHD stability theory is studied in order to gain an understanding of the effect of line-tying on an ideal MHD plasma before adding further complexities, and necessary and sufficient conditions are derived for the stability of force-free magnetic loops in the solar corona. The force-free basic state is discussed, and linear stability equations are derived. Attention is given to the boundary conditions used to simulate the line-tying effect of the dense photosphere. A very simple field structure is used to solve the stability equations analytically, the stability conditions obtained being verified by the energy principle. A method is presented for finding the stability of a general, cylindrically symmetric, force-free field, and results of an example are compared with the previous bounds obtained by Hood and Priest (1979, 1980).
Original languageEnglish
Pages (from-to)297-318
JournalGeophysical and Astrophysical Fluid Dynamics
Publication statusPublished - 1981


  • Coronal Loops
  • Force-Free Magnetic Fields
  • Magnetohydrodynamic Stability
  • Solar Corona
  • Solar Magnetic Field
  • Boundary Conditions
  • Boundary Value Problems
  • Linear Equations
  • Magnetic Field Configurations
  • Mathematical Models
  • Photosphere


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