Fine structure of convective motions in the solar photosphere

The granulation brightnesses and convective velocities in the solar photosphere between the levels of formation of the continuum radiation and the temperature minimum are examined. The properties of the brightness and velocity are analysed in a sixteen-column model. Four sorts of motions are most typical and efficient. In the first two, only the sign of the relative contrast of the material changes, which occurs, on the average, at a height of 270 km. In the last two motions, both the sign of the contrast and the direction of the motions are reversed near ~350 km. The convective motions maintain their column structure throughout the photosphere, right to the temperature minimum

The solar iron abundance: not the last word

Determinations of the solar iron abundance have converged to the meteoritic value with the Fe II studies of Holweger et al. (1990), Biémont et al. (1991) and Hannaford et al. (1992) and the Fe i results of Holweger et al. (1991). However, the latter authors pointed out that Blackwell et al. (1984) obtained a discordant result from similar oscillator strengths. A recent debate on this lingering discrepancy by the Oxford and Kiel contenders themselves has not clarified the issue. We do so here by showing that it stems from systematic differences between equivalent widths and oscillator strengths which masquerade as difference in fitted damping enhancement factors. We first discuss the various error sources in classical abundance determination and then emulate both sides of the debate with abundance fits of our own. Our emulation of the Oxford side shows that the abundance anomaly claimed by Blackwell et al. (1984) for solar Fe i 2.2 eV lines vanishes when equivalent width measurements from other authors are combined with better evaluation of the collisional damping parameter. On the Kiel side, we find that the oscillator strengths of Bard et al. (1991) used by Holweger et al. (1991) produce a suspicious trend when used to fuit solar Fe I lines, whereas comparable application of oscillator strengths from Oxford does not. The trend is mainly set by categories of Fe i lines not measured at Oxford; for lines of overlap the two sets agree and deliver the iron abundance value A Fe = 7.62 ± 0.04 which exceeds the meteorite value. The dissimilar lines may suffer from solar line-formation effects. We conclude that the issue of the solar iron abundance remains open. Definitive oscillator strengths are still needed, as well as verification of classical abundance determination by more realistic representations of the solar photosphere and of photospheric line formation

Bright features in the solar photosphere

We report thermodynamical properties of so-called “thermal plume” observed near the solar disc centre in 2001. The spectral observations of two iron lines analysed were obtained with the use of the Vacuum Tower Telescope (Tenerife)

Helioseismology space and ground-based studies

We give a preliminary report on the observations of solar irradiance fluctuations with the DIFOS photometer aboard the Russian–Ukrainian satellite CORONAS-F launched in 2001. In addition, the parallel ground-based spectral observations (VTT, Tenerife) carried out with 20-day observing space campaign are described