Mach-numbers in a simulation of convection in the sub-giant Eta Boo The mach-number is the local speed in units of the local sound speed, with values above 1 being super-sonic. The highest value in this particular snapshot is about 2.1 (the white spot). The blue areas on the surface correspond to the granules, the surface manifestation of the slow hot up-welling from the interior, and the red "lines" outline the edges of granules, with the cool down-drafts being squeezed in between. The simulation is about 36 by 36 by by 14 Mm (the Earth is about 6.4 Mm i radius).

ˆéRegner Trampedach, Robert F. Stein and & Aringke Nordlund.
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