Fr.: couronne F
The exterior part of the → solar corona, illuminated by solar light scattered or reflected by dust particles. The same phenomenon also produces the → zodiacal light, much farther away from the Sun. The dust particles are at most several microns in size and make up a disk stretching over almost 1 solar radius (700,000 km) from the Sun's surface. Unlike electrons, which are responsible for the → K corona, the dust particles move relatively slowly. Thus, the light scattered by them has the same spectrum as the → photosphere and shows the → Fraunhofer lines. The F corona is the most luminous part of the corona at 1.5 solar radii from the Sun's surface (M.S.: SDE).
F referring to the Fraunhofer lines; → corona.
The outermost part of Earth's atmosphere, a tenuous halo of hydrogen and some helium extending out to perhaps 15 Earth radii, which emits Lyman-alpha radiation when it is bombarded by sunlight.
interplanetary coronal mass ejections (ICME)
ešâneš-e andarsayyâreyi-ye jerm az tâj
Fr.: éjection de masse coronale interplanétaire
Fr.: couronne K
The inner part of the → solar corona which extends to about two solar radii. It is due to the → Thomson scattering of light from the → photosphere by the free electrons in the corona. The K corona exhibits a → linearly polarized continuous spectrum. The high speeds of the scattering electrons (on the average 10,000 km s-1 for a temperature of 2 million K) smear out the → Fraunhofer lines except the → H and K lines.
hurtâj, tâj-e xoršid (#)
Fr.: couronne solaire
The outermost atmosphere of the Sun immediately above the → chromosphere, which can be seen during a total solar eclipse. It consists of hot (1-2 × 106 K), extremely tenuous gas (about 10-16 g cm-3) extending for millions of kilometer from the Sun's surface.