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Astron. Astrophys. 324, 1183-1189

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Determination of physical parameters in dark mottles

G. Tsiropoula1 and B. Schmieder2

1National Observatory of Athens, Institute of Space Research, Lofos Koufos, GR-15236 Palea Penteli, Greece
2Observatoire de Paris, Section d'Astrophysique de Meudon, F-92195 Meudon Principal Cedex, France

Received 18 December 1996 / Accepted 26 Februaray 1997


The application of the cloud model to measurements of the contrast as a function of wavelength in the HFORMULA line has recently enabled us to derive numerical values for various parameters (such as velocity, source function, Doppler width and optical depth) of dark mottles observed near the center of the solar disk. The values of these parameters are used together with the calculations of Poland et al. (1971) and Yakovkin and Zel'dina (1975) in order to determine the physical conditions in these structures. Thus population densities at levels 1, 2, 3 (N1, N2, N3), total particle density of hydrogen NH, electron density Ne, electron temperature Te, gas pressure, total column mass, mass density and degree of hydrogen ionization can be determined. The values obtained are comparable with estimates obtained for spicules and mottles by different authors in the past and, furthermore, offer the prospect of putting observational constraints on non-LTE two-dimensional modelling of dark mottles observed in the H FORMULA line which is currently in progress.

Key words: Sun:chromosphere - fine structure - mottles - spicules

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© European Southern Observatory (ESO) 1997