Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 1978
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978natur.274...41a&link_type=abstract
Nature, vol. 274, July 6, 1978, p. 41, 42. Research supported by the Norges Almenvitenskapelige Forskningsrad.
Astronomy and Astrophysics
Astronomy
30
Infrared Astronomy, Solar Cycles, Sunspots, Umbras, Luminous Intensity, Magnetic Fields, Penumbras, Periodic Variations, Photometers, Scattering, Solar Activity, Spectroheliographs
Scientific paper
A variation in the infrared umbra intensity of large sunspots with the phase in the solar cycle is described. Dates, sizes, and heliographic latitudes are reported, as well as umbra and penumbra intensities at 1.67 microns for all large sunspots observed during 1968-1978. A graph of the umbra intensity as measured relative to the photospheric intensity at 1.67 microns for individual large sunspots as functions of epochs and a graph of the relative umbra intensity compared with the relative penumbra intensity for individual large sunspots are presented. The two graphs seem to indicate an epoch dependence both for the umbra and the penumbra. The time variation is such that the emitted intensity from sunspots increases with epoch during the solar cycle. When observations in other wavelength regions are taken into account, a 5% variation in the total flux from large sunspots during the cycle is estimated.
Albregtsen F.
Maltby Per
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