Photosphere/chromospheric signatures of solar variability: Magnetic coupling among solar atmospheric layers
Mausumi Dikpati (High Altitude Observatory, NCAR)
In this talk I review observational evidence of solar activity variability both on 'seasonal' (6-18 month periods) and decadal time scales seen in the solar photosphere and corona, and infer that it should also be present in the chromosphere as well, though there does not seem to have been much focus on finding it there. Ca-HK measures over a 70-year interval at Mt Wilson appear to show seasonal variations. Linkages among photosphere, chromosphere and corona are determined by both magnetic structures threading through them, and by vertical extension and propagation of various waves (acoustic, gravity, Alfven and Rossby). Seasonal variations are long enough that Rossby waves should be important for linking all these layers. The other waves will also be important for transmitting variable magnetic signals from the photosphere to higher levels; while models for them have a much longer history, solar Rossby waves are relatively new. I will discuss the possible linkages briefly. The chromosphere shows particular promise for revealing where in the solar atmosphere the most important seasonal and decadal variations in solar radiative outputs that drive space weather and climate are coming from.