Hopf bifurcations in coronal loops I. Stability conditions for static equilibrium

• Autores: Gómez, D.; Sicardi Schifino, A.; Ferro Fontán, C.
• Año de publicación: 1990
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Astrophys. J. 1990;352(1):318-325
• Materia: Hydromagnetics; Sun: corona
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

We study the coupling between the hot plasma confined in a coronal loop and the much colder chromospheric plasma at the footpoints. Considering the coronal heating rate as a control parameter, we find that the static equilibrium becomes unstable for heating rates below a critical value, giving rise to the appearance of a stable limit cycle. Starting from the hydrodynamic equations, we derive a model which generalizes the analysis of Kuin and Martens and consistently takes into account the condensation-evaporation process. In this paper, we linearize our equations in order to find the bifurcation point where the stability of the static equilibrium is lost. We also show that this model can provide a natural explanation for the excess widths of EUV spectral lines formed in the transition region. Moreover, we can predict the observed reduction in the broadening of these lines when they form in certain active regions, like quiescent prominences or sunspots.
Fil:Gómez, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Sicardi Schifino, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Ferro Fontán, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.