Chromospheres and transition regions

摘要: The existence of chromospheres on cool stars other than the Sun has been recognized for many years through presence emission components in Ca ii H and K lines He I 10 830 A. While some trends properties stellar as a function spectral type luminosity (e.g. Wilson—Bappu effect) were established basis optical data, field could not advance without observations at shorter wavelengths where chromo-spheric all easily observable produced by hotter material are located. potential was clear from developments solar physics. use balloons Kondo et al., 1972) rockets extended coverage to Mg h k (2803 2796 A, respectively), but satellites Copernicus TD—1) required observe down Ly α make broad surveys Weiler Oegerle, 1979 earlier references therein). combination fluxes profiles ii, allowed computation simple, spherically-symmetric chromospheric models extending up temperatures 8000 (see Part V). first evidence transition-region (20 000–200 000 K) came CMi (F5 IV–V) with (Evans 1975) TD—1 satellite (Jamar, Macon-Hercot Praderie 1976) Aur (F9 III + G6 III) (Dupree, rocket-borne payload (Vitz 1976). Emission-line observed space experiments especially valuable atmospheric modelling because they well calibrated absolute flux units.