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- Evershed_effect abstract "The Evershed effect, named after the British astronomer John Evershed, is the radial flow of gas across the photospheric surface of the penumbra of sunspots from the inner border with the umbra towards the outer edge.The speed varies from around 1 km/s at the border between the umbra and the penumbra to a maximum of around double this in the middle of the penumbra and falls off to zero at the outer edge of the penumbra.Evershed first detected this phenomenon in January 1909, whilst working at the Kodaikanal Solar Observatory in India, when he found that the spectral lines of sunspots showed doppler shift.Afterwards, measurements of the spectral emission lines emitted in the ultraviolet wavelengths have shown a systematic red-shift. The Evershed effect is common to every spectral line formed at a temperature below 105 K; this fact would imply a constant downflow from the transition region towards the chromosphere. The observed velocity is about 5 km/s. Of course, this is impossible, since if it were true, the corona would disappear in a short time instead of being suspended over the Sun at temperatures of million degrees over distances much larger than a solar radius.Many theories have been proposed to explain this redshift in line profiles of the transition region, but the problem is still unsolved, since a coherent theory should take into account all the physical observations: UV line profiles are redshifted on average, but they show back and forth velocity oscillations at the same time.In synthesis, the proposed mechanisms are: siphon flows in coronal loops driven by a pressure difference, different cross-sections of the coronal loops footpoints, the return of spicules, multiple flows, nanoflares, and thermal instabilities during chromospheric condensation.The effect was commemorated in a postage stamp issued in India on 2 December 2008.".
- Evershed_effect wikiPageID "2656271".
- Evershed_effect wikiPageRevisionID "604290968".
- Evershed_effect hasPhotoCollection Evershed_effect.
- Evershed_effect subject Category:Emission_spectroscopy.
- Evershed_effect subject Category:Plasma_physics.
- Evershed_effect subject Category:Solar_phenomena.
- Evershed_effect type Phenomenon100034213.
- Evershed_effect type PhysicalEntity100001930.
- Evershed_effect type Process100029677.
- Evershed_effect type SolarPhenomena.
- Evershed_effect comment "The Evershed effect, named after the British astronomer John Evershed, is the radial flow of gas across the photospheric surface of the penumbra of sunspots from the inner border with the umbra towards the outer edge.The speed varies from around 1 km/s at the border between the umbra and the penumbra to a maximum of around double this in the middle of the penumbra and falls off to zero at the outer edge of the penumbra.Evershed first detected this phenomenon in January 1909, whilst working at the Kodaikanal Solar Observatory in India, when he found that the spectral lines of sunspots showed doppler shift.Afterwards, measurements of the spectral emission lines emitted in the ultraviolet wavelengths have shown a systematic red-shift. ".
- Evershed_effect label "Efeito Evershed".
- Evershed_effect label "Evershed effect".
- Evershed_effect label "Evershed-Effekt".
- Evershed_effect label "Эффект Эвершеда".
- Evershed_effect label "埃弗谢德效应".
- Evershed_effect sameAs Evershed-Effekt.
- Evershed_effect sameAs Efeito_Evershed.
- Evershed_effect sameAs m.07vs_m.
- Evershed_effect sameAs Q1382125.
- Evershed_effect sameAs Q1382125.
- Evershed_effect sameAs Evershed_effect.
- Evershed_effect wasDerivedFrom Evershed_effect?oldid=604290968.
- Evershed_effect isPrimaryTopicOf Evershed_effect.