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The Sun's corona is much hotter (by a factor from 150 to 450) than the visible surface of the Sun: the corona's temperature is 1 to 3 million kelvin compared to the photosphere's average temperature – around 5 800 kelvin. The corona is far less dense than the photosphere, and produces about one-millionth as much visible light.
Density in the corona generally decreases with height above the visible "surface", or photosphere, meaning that lower-frequency emission is produced higher in the atmosphere, and the Sun appears larger at lower frequencies. This type of emission is most prominent below 300 MHz due to typical coronal densities, but particularly dense structures ...
The Sun is composed primarily of the chemical elements hydrogen and helium; they account for 74.9% and 23.8%, respectively, of the mass of the Sun in the photosphere.All heavier elements, colloquially called metals in stellar astronomy, account for less than 2% of the mass, with oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%) being the most abundant.
The slow solar wind has a velocity of about 400 kilometres per second (250 mi/s), a temperature of 2 × 10 5 K and a composition that is a close match to the corona. The fast solar wind has a typical velocity of 750 km/s, a temperature of 8 × 10 5 K and nearly matches the photosphere's.
Coronal loops begin and end at two footpoints on the photosphere and project into the transition region and lower corona. They typically form and dissipate over periods of seconds to days [ 1 ] and may span anywhere from 1 to 1,000 megametres (621 to 621,000 mi) in length.
The term variant of concern (VOC) for SARS-CoV-2, which causes COVID-19, is a category used for variants of the virus where mutations in their spike protein receptor binding domain (RBD) substantially increase binding affinity (e.g., N501Y) in RBD-hACE2 complex (genetic data), while also being linked to rapid spread in human populations ...
The moniker FLiRT is an acronym for the locations of the mutations the variants share on the virus' spike protein. HOW ARE THE FLIRT VARIANTS DIFFERENT FROM PREVIOUS VARIANTS? The FLiRT variants ...
During a total solar eclipse, the photosphere of the Sun is obscured, revealing its atmosphere's other layers. [1] Observed during eclipse, the Sun's chromosphere appears (briefly) as a thin pinkish arc, [11] and its corona is seen as a tufted halo. The same phenomenon in eclipsing binaries can make the chromosphere of giant stars visible. [12]