Bibcode
DOI
Díaz, A. J.; Oliver, R.; Ballester, J. L.
Referencia bibliográfica
The Astrophysical Journal, Volume 580, Issue 1, pp. 550-565.
Fecha de publicación:
11
2002
Revista
Número de citas
75
Número de citas referidas
63
Descripción
Some observations suggest that quiescent solar prominences can be
considered as composed by small-scale loops, or fibrils, which are
stacked one after another in both the vertical and horizontal
directions. In a previous work we studied, in Cartesian geometry, the
propagation of fast MHD waves in a two-dimensional magnetostatic model
representing one of these fibrils. Since this is a crude model to
represent a real fibril, in this paper we use a more realistic model
based on a cylindrically symmetric flux tube and study the propagation
of fast MHD waves in this structure. A new array of modes of
oscillation, together with their periods and spatial properties, is
described, showing several important differences with respect to the
properties of modes in Cartesian geometry. Among other conclusions, our
results show that all sausage modes (m=0) possess a cutoff frequency,
while the fundamental kink and fluting modes (m>0) do not show such a
cutoff. In addition, the frequency of these modes is independent of the
azimuthal wavenumber (m) and of the fibril thickness for a wide range of
values of this parameter, which is an important fact for prominence
seismology. Moreover, the spatial structure of the modes below the
cutoff frequency is such that in this geometry perturbations are
confined in the dense part of the fibril, the leakage of energy toward
the coronal medium being very small, which may prevent the excitation of
neighboring fibrils. Finally, diagnostic diagrams displaying the
oscillatory period in terms of some equilibrium parameters are provided
in order to allow for a comparison between our theoretical results and
those coming from observations.