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Evershed Effect in Sunspots and their Canopies

Published online by Cambridge University Press:  12 April 2016

S.K. Solanki ,
C. Montavon  and
W. Livingston
S.K. Solanki
Affiliation:
Institute of Astronomy, ETH-Zentrum, CH-8092 Zürich, Switzerland
C. Montavon
Affiliation:
Institute of Astronomy, ETH-Zentrum, CH-8092 Zürich, Switzerland
W. Livingston
Affiliation:
National Solar Observatory, NOAO*, P.O.Box 26732, Tucson AZ 85726, USA

Abstract

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An analysis of Stokes I and V profiles of 1.56 µm lines of sunspots near the solar limb shows that the magnetic field continues outside the visible contours of sunspots in the form of a low-lying superpenumbral canopy. We also find that the V profiles formed in the canopy exhibit the Evershed effect (with line shifts of 1–2 km s−1), while the matter below it shows no sign of a flow. Therefore, the Evershed effect definitely is present beyond the visible sunspot boundary. However, if we interpret the line shifts in terms of stationary flows, then only a small fraction of the matter seen to be flowing outwards in the penumbra can be accounted for by the outward flow in the superpenumbral canopy. Therefore, although the Evershed “flow” does not stop at the boundary of the spot, most of the flowing matter stops or disappears there.

Keywords

Solar Magnetic FieldsSunspotsevershed Flow
Type
Session 1. Structure of Active Regions
Information
International Astronomical Union Colloquium , Volume 141: The Magnetic and Velocity Fields of Solar Active Regions , 1993 , pp. 52 - 55
Copyright
Copyright © Astronomical Society of the Pacific 1993

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