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The red color of the chromosphere could be seen during the solar eclipse of August 11, 1999.. The density of the Sun's chromosphere decreases exponentially with distance from the center of the Sun by a factor of roughly 10 million, from about 2 × 10 −4 kg/m 3 at the chromosphere's inner boundary to under 1.6 × 10 −11 kg/m 3 at the outer boundary. [7]
For example, jetting phenomena observed in coronal and chromospheric temperatures are sometimes referred to as coronal jets and chromospheric jets (or chromospheric surges), respectively, and when observed in X-rays, extreme ultraviolet, white light, and Hα are sometimes referred to as X-ray jets, EUV jets, white-light jets, and Hα jets (or ...
An emission in white light is only seldom observed: usually, flares are only seen at extreme UV wavelengths and into the X-rays, typical of the chromospheric and coronal emission. In the corona, the morphology of flares is described by observations in the UV, soft and hard X-rays, and in Hα wavelengths, and is very complex.
Bart De Pontieu (Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, California, United States), Robert Erdélyi and Stewart James (both from the University of Sheffield, United Kingdom) hypothesised in 2004 that spicules form as a result of P-mode oscillations in the Sun's surface, sound waves with a period of about five minutes that causes the Sun's surface to rise and fall at ...
Chromospheric activity is signaled by the presence of emission cores in the Ca II H and K resonance lines. Balmer emission, or Hα, is also associated with active chromospheres. X-ray emission is known as a tracer for active coronal regions, and ultraviolet (UV) emission and flaring are, by solar analogy, known to be associated with stellar ...
They exhibit variations in their luminosity due to rotation of the star coupled with starspots, and other chromospheric activity. [1] Resultant brightness fluctuations are generally less than 0.5 magnitudes. Light curves of BY Draconis variables are quasiperiodic. The period is close to the star's mean rotational rate.
chromospheric activity index A parameter indicating the magnetic activity in a star's chromosphere. One measure of this activity is log R′ HK, where R′ HK is the ratio of the equivalent width of a star's singly ionized calcium H and K lines, after correction for photospheric light, to the bolometric flux. [4]
Sun's faculae. Dark regions are sunspots and the brighter speckled regions around them are faculae. Although image is in grayscale, it correctly presents true white color of Sun's photosphere.