List of Figures

View Image Figure 1:
The tripartite model from Jahn and Schmidt (1994) consists of three stratifications as sketched in the left panel: An umbra, a thick penumbra, and the quiet Sun. The umbra is thermally isolated and confined by a current sheet called peripatopause, while the penumbra is confined by a current sheet called magnetopause. For depths smaller than zbp the magnetopause transmits 70% of the quiet Sun heat flux, thereby accounting for the surplus brightness of the penumbra when compared to the umbra. The right panel shows a surface plot of the (logarithmic) magnetic pressure. Credit: Jahn and Schmidt (1994), reproduced with permission of the ESO.
View Image Figure 2:
Maps of intensity, LOS velocity, and circular polarization of sunspot (12 Nov 2006, 𝜃 = 30°) from Fe i 630.2 nm taken with the spectropolarimeter SP attached to the SOT onboard Hinode (courtesy of M. Franz, KIS).
View Image Figure 3:
The spot of NOAA 10933 observed with SP/Hinode at two different heliocentric angles: 𝜃 = 3° (left) and 47° (right). The upper row shows velocity maps inferred from the line wing of Fe i 630.15 nm. The bottom row shows so-called ‘Ichimoto’-grams, i.e., maps of Stokes V in the red wing of Fe i 630.25 nm, i.e., λ0 + 211 mA. The left spot is almost at disk center such that vertical motion and polarity reversals within the spot are best visible. The LOS into the right spot is inclined such that the horizontal flow component is dominant (courtesy of M. Franz, KIS).
View Image Figure 4:
Two types of 3-lobe-V-profiles. The left profile of Fe i 630.15 nm and Fe i 630.25 nm displays a lobe in the blue wing. The right profile displays a redshifted lobe of opposite sign, which is associated with a second zero crossing. The bump in the left profile can be interpreted as a blueshifted magnetized flow component, with the same polarity as the main profile. The bump in the right profile is a signature of a redshifted magnetic component, which is of opposite polarity as the main profile. The plotted profiles are from a spot at disk center, but are also measured in spots off disk center (courtesy of M. Franz, KIS).
View Image Figure 5:
Time evolution of an upflow plume developing into an umbral dot. The top panel shows the photospheric intensity appearance, clearly indicating bright umbral dots with central dark lanes, the middle panel shows vz in the range from –1.2 to 4.1 km s–1 and the bottom panel the vertical field strength Bz in the range from –0.3 to 3.8 kG. The horizontal/vertical extent of the cuts are 820 km / 1.4 Mm, respectively. This figure is reproduced from Schüssler and Vögler (2006) by permission of the AAS.
View Image Figure 6:
Continuum intensity image at 630 nm of the simulated sunspot of Rempel et al. (2009b) and its environment (doubled in the y-direction). The bright umbral dots and penumbral filaments have peak intensities between 40% and 90% of the average value outside the spot. The penumbral filaments reach lengths of 2 – 3 Mm. The white frame indicates a filament studied in more detail in Figure 7. This figure is reproduced from Rempel et al. (2009b) by permission of the AAS.
View Image Figure 7:
Vertical cuts perpendicular through the filament shown in Figure 6. The dark lines indicate the levels of τ630 = 1.0, 0.1, and 0.01, respectively. The filaments has an overall reduced field strength close to 1 kG and shows a strong increase of the inclination angle with values exceeding 80°, while the background field has an average inclination close to 40°. The τ levels are lifted by about 200 km due to the strong central upflow of plasma reaching values up to −1 vz ≈ 2 km s. Horizontal flows perpendicular to the filament (vy) show a weak indication of roll-type convection. Horizontal flows along the filament axis are dominated by outflows with amplitudes close to vx ≈ 2 km s−1. This figure is reproduced from Rempel et al. (2009b) by permission of the AAS.
Watch/download Movie Figure 8: (mov-Movie; 17203 KB)
Movie: Rosseland mean intensity (grey RT) image from the simulation run presented in Rempel et al. (2009a). Displayed is the sunspot pair after about 5.75 hours of temporal evolution (3.75 hours in high resolution). The sunspot on the left has more umbral dots due to the overall weaker field strength (3 kG), most extended outer penumbra can be found in the center region with the shortest separation between the opposite polarity spots.
Watch/download Movie Figure 9: (mov-Movie; 6617 KB)
Movie: Top: Vertical magnetic field (magnetogram) at the τRoss = 1 level for the snapshot displayed in Figure 8. Magnetic field values are from –3 to 3 kG. Bottom: Magnetic field strength on vertical cut through the center of both sunspots. Values are from 0 to 10 kG.
View Image Figure 10:
Relation between horizontal outflows from sunspots and the average field inclination. The red line (left scale) shows the velocity in the x-direction, the blue line (right scale) the inclination angle (both averaged between y = 20.5 Mm and y = 28.5 Mm and one hour in time). Vertical dotted lines indicate the inner and outer boundaries of regions with strong coherent outflows from the spots. Outflows start where the inclination angle exceeds 45°.
Watch/download Movie Figure 11: (mov-Movie; 11637 KB)
Movie: Penumbral fine structure at τ = 1 level. The intensity image (panel a) shows radially aligned filaments that correspond to regions with moderately enhanced horizontal field (b) and strongly reduced vertical field (c). The result is a strong variation in field inclination (d). Fast radial outflows (e) with velocities of about 8 km s–1 within flow channels are present along horizontal stretches of field. The vertical velocity (f) shows upflows mostly along the center of individual filaments and downflows near their edges in lateral direction. Downflows are also found near the outer end, where the inclination exceeds 90°, indicating magnetic flux returning beneath the surface. Contour lines in (e) and (f) highlight outflows faster than 10 km s–1 and downflows faster than 5 km s–1. This figure is reproduced from Rempel (2011a) by permission of the AAS.
View Image Figure 12:
Correlations between horizontal (Evershed) flow and intensity (a) and magnetic field strength (b). In the inner penumbra outflows are preferentially found in bright features, the correlation essentially disappears toward outer penumbra and turns weakly negative. The magnetic field strength is reduced in flow channels in the inner penumbra, but enhanced in the outer penumbra.
View Image Figure 13:
Rosseland mean intensity image from the currently best resolved sunspot simulation. The grid resolution is 16 km in the horizontal and 12 km in thevertical direction. This figure is reproduced from Rempel (2011b) by permission of the IAU.
Watch/download Movie Figure 14: (mov-Movie; 46891 KB)
Movie: Results from a flux emergence simulation in a 92 × 49 × 8 Mm3 sized simulation domain. Top: Magnetogram at τRoss = 0.1. Bottom: Magnetic field strength on vertical cut along the indicated red dashed line. The presented snapshot at 15.3 hours after initialization of the simulation run shows the formation of a pair of opposite polarity spots with about 3 × 1021 Mx flux. This figure is reproduced from Cheung et al. (2010) by permission of the AAS.
View Image Figure 15:
Snapshots in the G band of a spot on July 4, 2009, as it develops a penumbra. The spot is located at 𝜃 = 28° and was observed from 08:32 UT until 13:03 UT at the German VTT in Tenerife (Schlichenmaier et al., 2010b). Flux emergence takes place in the lower right corner of the images. Flux patches of the spot polarity are observed to migrate towards and merge with the spot. As the area and the magnetic flux of the spot increases the penumbra forms on the side opposite to the flux emergence.
View Image Figure 16:
Continuum image (left) and velocity map (right) of a sunspot at 𝜃 = 35° (N34W5) observed with HMI/SDO on January 6, 2011 (12-min average). The Evershed flow within the penumbra and the moat flow in the spot surroundings. The contour marks the outer spot boundary, the arrow points towards disk center, and the tick marks are in arcsec (courtesy of J. Löhner-Böttcher, KIS).