A solar flare is a tremendous explosion on the Sun that happens when energy stored in ‘twisted’ magnetic fields (usually above sunspots) is suddenly released.
In a matter of just a few minutes they
heat material to many millions of degrees and produce a burst of radiation
across the electromagnetic spectrum, including from radio waves to x-rays and
gamma rays.
Scientists classify solar flares
according to their brightness in the x-ray wavelengths. There are three
categories: X-class flares are big; they are major
events that can trigger radio blackouts around the whole world and long-lasting
radiation storms in the upper atmosphere.
M-class
flares are medium-sized;
they generally cause brief radio blackouts that affect Earth’s polar regions.
Minor radiation storms sometimes follow an M-class flare.
Compared to X- and M-class events, C-class
flares are small with few noticeable consequences here on
Earth.
Solar flares are different to ‘coronal mass ejections’ (CMEs), which were
once thought to be initiated by solar flares. CMEs are huge bubbles of gas
threaded with magnetic field lines that are ejected from the Sun over the
course of several hours. Although some are accompanied by flares, it is now
known that most CMEs are not associated with flares.
This has important implications for understanding and predicting the
effects of solar activity on the Earth and in space. If a CME collides with the
Earth, it can excite a geomagnetic storm.
Large geomagnetic storms have, among other things, caused electrical power
outages and damaged communications satellites. The energetic particles driven
along by CMEs can be damaging to both electronic equipment and astronauts or
passengers in high-flying aircraft.
Solar flares, on the other hand, directly affect the ionosphere and radio
communications at the Earth, and also release energetic particles into space.
Therefore, to understand and predict ‘space weather’ and the effect of solar
activity on the Earth, an understanding of both CMEs and flares is required.
Image & info via ESA
Source: What are solar flares? – Scents of Science (myfusimotors.com)
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