Loss of equilibrium in coronal loops

The loss of equilibrium in coronal magnetic field structures is a possible source of energy for coronal heating and solar flares. It is investigated whether such a loss of equilibrium occurs when a coronal loop is progressively twisted by photospheric motions. In studies of 2D cylindrical equilibria, long loops have been found to be of constant cross-sectional area along most of their length, with axial variations being confined to narrow boundary layers. This information is used to develop a 1D line-tied model, for a 2D coronal loop. A twisted loop with a non-zero plasma pressure is also examined. The loss of equilibrium is only found at high-plasma beta. It is conjectured that such high-beta can occur in flare loops and prior to a prominence eruption. However, when the plasma evolves adiabatically, there is no loss of equilibrium.