Accession Number : AD0725928

Title :   The Velocity Field in Sunspots,

Corporate Author : OSLO UNIV (NORWAY) INST OF THEORETICAL ASTROPHYSICS

Personal Author(s) : Maltby,P.

Report Date : 1970

Pagination or Media Count : 17

Abstract : In 1909, Evershed at Kodaikanal Observatory in India observed the first spectra showing displacements of the Fraunhofer lines in the penumbra of sunspots. Evershed suggested that the line shift was a Doppler displacement of the lines, caused by an ordered motion in the sunspot. From observations in different parts of the visible spectrum several authors have confirmed the Doppler displacements hypothesis. With the Doppler shift interpreted as a material motion, the observations show that the velocity is directed from the spot umbra towards the photosphere in the deeper layers of the spot. It has been shown that there is a considerable fine-structure in the velocity field; some parts of the sunspot material seem to be in rapid motion, whereas neighbouring parts show little or no line displacement. Further, from observations at different heights it appears that the velocity field changes character as one moves from deeper to higher layers in the sunspot atmosphere. Recently, the interpretation based on material motion has been questioned and it has been suggested that magneto-acoustical waves may account for the observations. (Author)

Descriptors :   (*SUNSPOTS, MOTION), SOLAR RADIATION, DOPPLER EFFECT, SOLAR SPECTRUM, MAGNETIC FIELDS, SPECTRUM ANALYZERS, NORWAY

Subject Categories : Astrophysics

Distribution Statement : APPROVED FOR PUBLIC RELEASE