A solar flare is a violent explosion in the Sun’s atmosphere with an energy equivalent to tens of millions of hydrogen bombs.
Solar flares take place in the solar corona and chromosphere, heating plasma to tens of millions of kelvins and accelerating the resulting electrons, protons and heavier ions to near the speed of light.
They produce electromagnetic radiation across the electromagnetic spectrum at all wavelengths from long-wave radio to the shortest wavelength gamma rays.
Most flares occur around sunspots, where intense magnetic fields emerge from the Sun’s surface into the corona.
The energy efficiency associated with solar flares may take several hours or even days to build up, but most flares take only a matter of minutes to release their energy..
In astronomy, a corona is the luminous plasma “atmosphere” of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph..
Solar radiation is radiant energy emitted by the sun, particularly electromagnetic energy.
About half of the radiation is in the visible short-wave part of the electromagnetic spectrum.
The other half is mostly in the near-infrared part, with some in the ultraviolet part of the spectrum .
The portion of this ultraviolet radiation that is not absorbed by the atmosphere produces a suntan or a sunburn on people who have been in sunlight for extended periods of time..
A sunspot is a region on the Sun’s surface (photosphere) that is marked by a lower temperature than its surroundings and intense magnetic activity, which inhibits convection, forming areas of low surface temperature.
Although they are blindingly bright at temperatures of roughly 4000-4500 K, the contrast with the surrounding material at some 5700 K leaves them clearly visible as dark spots.
If they were isolated from the surrounding photosphere they would be brighter than an electric arc.
Sunspot numbers have been recorded since 1700 AD and estimated back to 11,000 BP.
The recent trend is upward from 1900 to the 1960s, then somewhat downward.
The Sun was last similarly active over 8,000 years ago..
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