The Evershed effect in sunspots as a siphon flow along a magnetic flux tube

DOI: 
Publication date: 
04/12/1997
Main author: 
Montesinos, B
IAA authors: 
Authors: 
Montesinos, B; Thomas, JH
Journal: 
NATURE
Publication type: 
Article
Volume: 
390
Pages: 
485-487
Number: 
Abstract: 
The Evershed effect(1)-a wavelength shift and profile asymmetry in the spectral lines observed from the outer regions of sunspots (the penumbra)-has been interpreted as a radial outflow of gas from the sunspot, but the dynamics of the now have not been fully understood(2). Although the Evershed effect seems to stop abruptly at the outer edge of the penumbra, the outflow itself must continue, though tracing its path has proved difficult. Theoretical(3,4) and observational(5-7) studies have suggested that much of the continuing now may follow magnetic field lines that go below the visible surface of the Sun at or just beyond the edge of the penumbra, and recent observations have now confirmed this picture(8). Here we show, using theoretical calculations based on a more realistic model, that the flow acts like a siphon(3,9-12) which is driven along a magnetic nux tube by the pressure drop between the endpoints of the tube.
Database: 
WOK
Keywords: