fredag 4 september 2009
Are Sunspots Disappearing?
A sunspot is an area on the Sun's surface (photosphere) that is marked by intense magnetic activity, which inhibits convection, forming areas of reduced surface temperature. They can be visible from Earth without the aid of a telescope. Although they are at temperatures of roughly 4,000–4,500 K, the contrast with the surrounding material at about 5,800 K leaves them clearly visible as dark spots, as the intensity of a heated black body (closely approximated by the photosphere) is a function of T (temperature) to the fourth power. If a sunspot were isolated from the surrounding photosphere it would be brighter than an electric arc. Short wave communacation is effected of sunspots. A low munber of sunspots are good.
Read a report from NASA >>>
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