White Light Sunspot Observations from the Solar Optical Universal Polarimeter on Spacelab-2

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Science  27 Nov 1987:
Vol. 238, Issue 4831, pp. 1264-1267
DOI: 10.1126/science.238.4831.1264


The flight of the Solar Optical Universal Polarimeter on Spacelab-2 provided the opportunity for the collection of time sequences of diffraction-limited (0.5 are second) solar images with excellent pointing stability (0.003 are second) and with freedom from the distortion that plagues ground-based images. A series of white-light images of active region 4682 were obtained on 5 August 1985, and the area containing the sunspot has been analyzed. These data have been digitally processed to remove noise and to separate waves from low-velocity material motions. The results include (i) proper motion measurements of a radial outflow in the photospheric granulation pattern just outside the penumbra; (ii) discovery of occasional bright structures ("streakers") that appear to be ejected outward from the penumbra; (iii) broad dark "clouds" moving outward in the penumbra, in addition to the well-known bright penumbral grains moving inward; (iv) apparent extensions and contractions of penumbral filaments over the photosphere; and (v) observation of a faint bubble or looplike structure that seems to expand from two bright penumbral filaments into the photosphere.