Moat flow system around sunspots in shallow subsurface layers

Abstract

We investigate subsurface moat flow system around symmetrical sunspots of McIntosh type H and compare it to the flow system within supergranular cells. Representatives of both types of flows are constructed by means of statistical averaging of flow maps obtained by time--distance helioseismic inversions. We find that moat flows around H-type sunspots replace the supergranular flows but there are two principal differences between the two phenomena: The moat flow is asymmetrical, probably due to proper motion of sunspots with respect to the local frame of rest, while the flow in the supergranular cell is highly symmetrical. Further, the whole moat is a downflow region, while the supergranule contains the upflow in the centre, which turns into the downflow at some 60 % of the cell radius from its centre. We estimate that the mass downflow rate in the moat region is at least two times larger than the mass circulation rate within the supergranular cell.

24 pages, 7 figure, accepted for publication in ApJ

References in corpus (10)

• Radiative MHD simulation of sunspot structure
• Penumbral structure and outflows in simulated sunspots
• Subsurface magnetic field and flow structure of simulated sunspots
• Validated helioseismic inversions for 3-D vector flows
• Downflows in sunspot umbral dots
• Flow Field Evolution of a Decaying Sunspot
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• Correlations between sunspots and their moat flows
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Cited by in corpus (11)

• Numerical simulations of sunspot decay: On the penumbra -- Evershed flow -- moat flow connection
• Restoring process of sunspot penumbra
• Issues with time--distance inversions for supergranular flows
• Sensitivity kernels for inferring Lorentz stresses from normal-mode frequency splittings in the Sun
• On the extent of the moat flow in axisymmetric sunspots
• Evolution of the flow field in decaying active regions, Transition from a moat flow to a supergranular flow
• Average solar active region: I. Intensities, velocities, and the photospheric magnetic field
• Statistical analysis of acoustic wave power and flows around solar active regions
• One-sided arc averaging geometries in time-distance local helioseismology
• Testing volume integrals of travel-time sensitivity kernels for flows
• Evolution of solar surface inflows around emerging active regions