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Astron. Astrophys. 358, 575-582 (2000)

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3. Results

In Figs. 2-4 we present the basic results of our calculations. The upper panels show the modelled non-thermal velocity distribution and the calculated electron density. The reminding panels show line profiles for four lines; H [FORMULA], H [FORMULA], H 08 and Na_I D.

[FIGURE] Fig. 2. The upper left panel shows models of constant non-thermal velocity. The upper right panel shows the final distribution of the electron density throughout the atmosphere while the middle panels show the line profiles of H [FORMULA], H [FORMULA] and the lower panels show the line profiles of H 08 and Na I D.

[FIGURE] Fig. 3. Same as Fig. 2 except for the models of non-thermal velocity as a fraction of the sound speed. Solid line ([FORMULA]), dotted line ([FORMULA]), dashed line ([FORMULA]) and dot-dash line ([FORMULA]) and long dashed line ([FORMULA]).

[FIGURE] Fig. 4. Same as the Fig. 2 for the third type of non-thermal velocity distribution.

3.1. Constant velocity

From Fig. 2 we can see that there is a lowering of the electron density with increasing non-thermal velocity. Also, with the increase of non-thermal velocity, the H [FORMULA] line shows a deeper self-reversal, while H [FORMULA] and H 08 change from emission to absorption.

In the Sodium doublet there are changes in the shape of the line wings with the lines becoming narrower with increasing non-thermal velocity. For turbulent velocities equal to or greater than 5 km s-1, the line wings change dramatically.

3.2. Non-thermal velocity proportional to sound velocity

We can again see that the electron density is changed with changes in the level of the non-thermal velocity. By changing the non-thermal velocity from [FORMULA] to [FORMULA] we manage to change the H [FORMULA] profile from emission with the self-reversal to pure absorption. H [FORMULA] and H 08 both have a very small emission component even with a non-thermal velocity of [FORMULA] and both lines again change their character similar to H [FORMULA].

The Sodium doublet again shows changes in the line shape. We attribute these changes to changes in the electron density in the photosphere. With an increase in the non-thermal velocity, the central emission in the lines weakens and in the case when the non-thermal velocity equal [FORMULA], almost completely disappears. There is a large increase in the intensity of the Na I wings with increasing turbulent velocity in the photosphere.

3.3. Linearly increasing non-thermal velocity in the upper chromosphere

In the chromosphere/transition region, changes in the electron density are in agreement with Eq. (2). Again there are dramatic changes in the shape of the Balmer lines. H [FORMULA] shows the most prominent changes - from emission in the case of a low non-thermal velocity to deep absorption with an increase in the level of the non-thermal velocity.

The wings of the Sodium doublet stay almost unchanged, which is easily explained by the constant non-thermal velocity in the photosphere. Again the emission core of the D line changes from being very prominent to almost non-existence with increasing non-thermal velocity in the chromosphere.

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© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000