Bibcode
Al, N.; Bendlin, C.; Hirzberger, J.; Kneer, F.; Trujillo Bueno, J.
Referencia bibliográfica
Astronomy and Astrophysics, v.418, p.1131-1139 (2004)
Fecha de publicación:
5
2004
Revista
Número de citas
18
Número de citas referidas
11
Descripción
This investigation is based on Hα observations of high spatial
resolution. They stem from an enhanced network region near disk centre
of the sun and consist of broad-band and narrow-band images taken with
the two-dimensional ``Göttingen'' Fabry-Perot spectrometer mounted
in the Vacuum Tower Telescope at the Observatorio del Teide/Tenerife.
The ``lambdameter method'' was applied to derive intensity and velocity
maps over the two-dimensional field of view reflecting the behaviour of
these parameters in the solar chromosphere. The determination of the
source function, the line-of-sight (LOS) velocity, the Doppler width and
the optical depth was based on Beckers' cloud model (Beckers
cite{beckers}). From the LOS velocity distribution along the Hα
structures we conclude that ballistic motions are unlikely to prevail.
Especially the bright Hα features cannot be explained by the cloud
model. It is shown how, instead, two-dimensional non-LTE radiative
transfer calculations of embedded chromospheric structures lead to
reasonable agreement with the observed line profiles from these bright
features. It is found that many of the bright fibril-like structures
near dark fibrils can be explained by radiation which is blocked by
absorbing material at large heights and escapes through less opaque
regions. We estimate the number densities and the temperature. With
these and with the measured velocities, the kinetic energy flux and the
enthalpy flux related to the motions of the fine structures can be
calculated. Both fall short by at least an order of magnitude of
covering energy losses by radiation of active chromospheric regions.