1. Photospheric Flows and Structures Mark Rast Laboratory for Atmospheric and Space Physics Department of Astrophysical and Planetary Sciences University of Colorado, Boulder LoHCo meeting -- Boulder, Colorado 7 November 2006 PSPT, 2 July 2005, CaIIK Granulation Mesogranulation Supergranulation Giant cells Meridional flow Differential rotation Flux elements Network Plage/faculae Pores Sunspots Coronal holes Polar fields

2. Dutch Open Telescope G-band CaIIH PSPT 20 March 2001 1731UT 393.5nm Granulation (Herschel 1801) 1000km scale 1000m/s vertical flow 0.2hr lifetime Supergranulation (Hart 1954, Leighton et al. 1962) 32000km scale 400m/s horizontal flow 20hr lifetime Courtesy D. Hathaway (NASA Marshall) Direct Doppler signal

3. Mesogranulation? Supergranulation Granulation Little sign of the global scale motions (giant cells)? (November et al. 1981) 5000km scale 60m/s vertical flow 3hr lifetime Shine et al. 2000 Hathaway et al. 2000 November et al. 1981

4. Two contributions: thermal energy and ionization energy What controls granular dynamics?

5. courtesy Nesis (Rast 1995) simulation of Nordlund and Stein (Rast et al. 1993) Foukal 1990

6. 3D plume width 31.2% granules fragment (Hirzberger et al. 1999) 3D plume width 50% granules fragment Yes under the influence of mutual advection and merger (Rast 2003). Can a random collection of short-lived small-scale downflows interact to produce a large-scale long-lived pattern?

7. Both a low and high amplitude excess develop (mesogranulation and supergranulation) Convective scale selection is a top down process (convective pattern originate in photospheric boundary layer) “mesogranulation” “supergranulation” Anderson, D.K., Rast, M.P., Nordlund, Å., Stein, R.F. (2006) 2Mm16Mm8Mm4Mm

8. Does this highly reductionistic model have any relevance? Cattaneo et al. 2001 Dutch Open Telescope G-band CaIIH No monolithic downflows observed at the supergranular vertices. What is the role of the magnetic field?

9. Kosovichev, A.G., 2002, AN 323, 186. Rast et al, 1999, Nature 401, 678.

10. Steiner, O. et al., 1998, ApJ 495, 468. Steiner, O., 2005, A&A 430, 691.

11. Criscuoli, S. 2006 Low density cool region cools surroundings because source source function is suppressed Low density region in thermal equilibrium at depth heats surroundings because of the opacity reduction along ray paths.