The SOHO-Stellar Connection

摘要: The’ solar-stellar connection’ bridges the daytime and nighttime communities; an essential link between singular, but detailed, views of our Sun, broad, coarse, glimpses distant stars. One area in particular — magnetic activity has profited greatly from two way traffic ideas. In that spirit, I present evolutionary context for coronal activity, focusing on very different circumstances low-mass main-sequence stars like compared with more massive The former are active mainly early their lives, whereas latter become only near end theirs, during brief incursion into cool half Hertzsprung-Russell diagram as yellow, then red, giants. describe tools at disposal stellar astronomer; especially spectroscopy ultraviolet X-ray bands where coronae leave most obvious imprints. compare HST STIS spectra solar-type dwarfs ζ Dor (F7 V), source, α Cen A (G2 twin Sun to SOHO SUMER UV solar atlas. also line profiles dwarf corresponding features mixed ‘hybrid chromosphere’ bright giant TrA (K2II) archetype ‘non-coronal’ red Arcturus (α Boo; K2 III). shows dramatic evidence a ‘cool absorber’ its outer atmosphere is extinguishing ‘hot lines’ (like SiIV λ1393 Nv λ1238) below about 1500 A; corona seems lie beneath extended chromosphere, rather than outside Sun. taste moderate resolution we can expect recently launched Chandra Observatory (CXO), contemporaneous high measurements CXO calibration star Capella Aur; G8 III + Gl Last, preliminary results May 1999 observing campaign involving SUMER, TRACE, Kitt Peak Infrared Imaging Spectrometer (IRIS). purpose was explore dynamics quiet through key ‘magnetic transition zone’ separates kinetically dominated deep photosphere magnetically regime. Linking spatially temporally resolved phenomena properties average shapes (widths, asymmetries, intensity ratios, Doppler shifts) crucial step carrying physical insights setting realm