Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1985
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985a%26a...142..205k&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 142, no. 1, Jan. 1985, p. 205-211. Sponsorship: Deutsche Forschungsgemeinschaf
Astronomy and Astrophysics
Astrophysics
24
Astronomical Maps, Photosphere, Sunspots, Velocity Distribution, Astronomical Observatories, Coriolis Effect, Doppler Effect, Spatial Resolution, Time Lag
Scientific paper
Using the two-dimensional diode array system at the Locarno solar observatory, velocity and asymmetry maps of several sunspots were measured in the photospheric nonsplit 4.2-V line Fe 7090.4. It is found that the velocity and asymmetry contours of individual spots correspond very well. The Evershed velocity field taken from Doppler displacements of the very line core does not show any discontinuity at the penumbra borders. Velocity maxima are usually found very close to the outer spot border. The largest horizontal velocities are obtained at smallest heliocentric angles observed (25 deg), thus indicating a very steep velocity increase with depth. From time series of identical sunspots a slow temporal development of the Evershed field is seen, indicating a time delay with respect to the development of the visible spot structure. The vertical upflow needed to feed the observed horizontal flux is estimated to be of the order of 20-100 m/s.
Kueveler G.
Wiehr Eberhard
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