The three-dimensional structure of sunspots II. The moat flow at two different heights

Abstract

Many sunspots are surrounded by a radial outflow called the moat flow. We investigate the moat flow at two different heights of the solar atmosphere for a sunspot whose magnetic properties were reported in the first paper of this series. We use two simultaneous time series taken with the Transition Region And Coronal Explorer (TRACE) in white light and in the UV at 170 nm. The field-of-view is centered on the small sunspot NOAA 10886 located near disk center. Horizontal velocities are derived by applying two different local correlation tracking techniques. Outflows are found everywhere in the moat. In the inner moat, the velocities from the UV series are larger than those from white light, whereas in the outer part of the moat we find the converse result. The results imply that the white light velocities represent a general outflow of the quiet sun plasma in the moat, while UV velocities are dominated by small bright points that move faster than the general plasma flow.

Manuscript accepted by Astronomy & Astrophysics

References in corpus (5)

• Flow Field Evolution of a Decaying Sunspot
• Magnetic Flux Loss and Flux Transport in a Decaying Active Region
• Moat flow in the vicinity of sunspots for various penumbral configurations
• On the Moat-Penumbra Relation
• The velocity structure of moving magnetic feature pairs around sunspots: support for the U-loop model

Cited by in corpus (11)

• Subsurface magnetic field and flow structure of simulated sunspots
• Horizontal flow fields observed in Hinode G-band images II. Flow fields in the final stages of sunspot decay
• Local Helioseismology of Sunspots: Current Status and Perspectives (Invited Review)
• Correlations between sunspots and their moat flows
• Direct measurement results of the time lag of LOS-velocity oscillations between two heights in solar faculae and sunspots
• Moat flow system around sunspots in shallow subsurface layers
• Horizontal flow fields observed in Hinode G-band images III. The decay of a satellite sunspot and the role of magnetic flux removal in flaring
• 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
• The Current State-Of-The-Art In Active Region Seismology
• Velocity fields in and around sunspots at the highest resolution