N. Chromospheric models in solar-type stars

The intensity of that emission increased in response to the amount of non-thermal heating of the chromosphere.

A widely used indicator of chromospheric activity, the S index, was produced using the fluxes in those two lines.

That gap in chromospheric emission, called the Vaughan-Preston gap, existed for stars in the range 0.45 < B-V < 1.

Different chromospheric models for stars with the same B-V as the Sun (B-V = 0.65) had been computed to investigate whether the Vaughan-Preston gap was due to the response of the Ca II lines to different changes in the chromospheric temperature with height.

To date, surveys of Ca II emission in the solar neighbourhood seemed to reveal a bimodal distribution in which most stars had weak chromospheric emission, as does the sun; some active ones had high levels of emission and only a few had intermediate levels.

The Workshop focused on the following topics: (a) the status of preparations for the International Heliophysical Year, including for the United Nations Basic Space Science initiative, at the national, regional and international levels; (b) solar surface phenomena; (c) dynamics of the chromosphere and transition region; (d) coronal studies; (e) corona and interplanetary medium; (f) terrestrial atmosphere; (g) non-extensive statistical mechanics; (h) International Heliophysical Year/United Nations Basic Space Science instrument donors; (i) International Heliophysical Year/United Nations Basic Space Science instrument hosts; (j) International Heliophysical Year science in developing nations; and (k) astrophysical data systems and virtual observatories.