2-12-2008: Centenary of the Discovery of the Evershed Effect Indian Stamp

120.00

The Evershade effect, named after British astronomer John Evershed, is a radial flow of gas across the photosphere surface of sunspots in the penumbra along the fringes from the inner boundary to the outer edge. The speed varies between about 1km/s at the boundary between the penumbra and the penumbra, almost doubles in the middle of the penumbra, and becomes zero at the outer edge of the penumbra. In 1909, Evershed first detected this phenomenon while working at the Solar Observatory in India. He saw that the spectral lines of sunspots showed Doppler shifts showing. Which systematic redistribution of the spectral emission lines emitted at ultraviolet wavelengths.

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