Thermal Convection, Magnetic Field, and Differential Rotation in Solar-type Stars by Hideyuki Hotta

Author:Hideyuki Hotta
Language: eng
Format: epub, pdf
Publisher: Springer Japan, Tokyo

Fig. 3.2The radial velocity () in the case H0 on the orthographic projection

3.3 Results

3.3.1 Structure of Convection and Magnetic Field

Figure 3.1 shows the RMS velocities in the case H0, H1, and H2. The maximum RMS velocity is at the top boundary in the case H0. Since the Mach number determined with the reduced speed of sound is always under 0.3 all over the convection zone, the requirement for the validity of the RSST in this study is well satisfied (Hotta et al. 2012b).

Figure 3.2 shows the radial velocity () around the top boundary in the case H0 (, which is 7 Mm below the photosphere) in the orthographic projection. Note that since the shown location is close to the impenetrable top boundary, the value of the radial velocity is rather small. Since near the upper boundary the pressure scale height is less than 2 Mm, the convection pattern shows small cells of about ( ). The typical cell size is slightly smaller than supergranulation that is observed on the photosphere. This is the first work that well resolves the 10 Mm-scale convection pattern in a calculation of the solar global convection zone. Figure 3.3a–c shows the radial velocity at , , and in the case H0 by using the orthographic projection. In deeper layer the pressure scale height increases and the convection pattern becomes larger. The detailed analysis using the spherical harmonic expansion of the convective structure is shown in Sect. 3.3.3.

Fig. 3.3The radial velocities () are shown at (a, d, g), (b, e, h) and (c, f, i). The results in the cases H0, H1, and H2 are shown in (a–c), (d–f), and (g–i), respectively. The black circle around each panel show the location at

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