system
Given the following post, respond as if you're commenting on Reddit:
human
Can someone please explain solar flares? How large are they and how long do they last?
gpt
To be brief on what is an amazingly deep field:

Solar flares are the visible manifestations of magnetic explosions in the upper atmospheres of the Sun. Where a chemical explosion takes chemical potential energy and turns it into heat, a flare takes magnetic potential and turns it into heat (among other forms of energy).

Where this energy stored is in the complexity of the field. Generally more complex, tangled fields have a higher energy density. When a set of circumstance that are quite subtle are reached then a previously complicated magnetic field configuration can relax via a process called 'magnetic reconnection' into a more simple field.

The excess energy is converted into other forms such as thermal energy of the solar plasma and into high energy, non-thermal beams of particles. These hot gasses glow brightly and these particle beams generate high-energy photons.

It is this radiation that is the flare.

They are big events but they do vary in size over many orders of magnitude. The flares we see are classified by an array of satellites called GOES. The classes from smallest to biggest are A,B,C,M,X. Each class represents a ten times increase in luminosity from the class before. We also expect that flares can be significantly smaller than we have a hope of detecting. In fact such small flares, called nano-flares could be much more common than any other type.

An X-class flare can be extremely luminous across the spectra (from radio to gamma-ray). Such a flare can release over 10^25 Joules over the course of a few seconds up to maybe an hour. In energy terms that is something like 100 billion megatons.

In terms of physical size the site of the explosion is not really resolved, it is quite small compared to the sizes we deal with when it comes to the Sun. However, we can observe the region which is heated and the region which beams of particles impact (the footpoints) and all these scales are vast, many times the size of the Earth.