Just a few planetary steps away in our immediate neighborhood, the Sun sits as a typical average astrophysical star: a factory that burns Hydrogen into Helium through nuclear fusion. Basically, an H-bomb in empty space. Fusion is the process by which two atomic nuclei, in this case those of Hydrogen, fuse and form a new atomic nucleus, in this case that of Helium. The Helium nucleus has less energy that the initial products; the difference in energy is emitted away as radiation; we say the Sun shines... The Sun has been around for around 5 billion years. And it is expected to exhaust its Hydrogen fuel within the next 5-6 billion. So, it is middle aged and has started graying; and like most middle aged people, it goes through periods of crisis we call solar flares (this is starting to get too personal, but I'll try to carry on). We expect that at the end of its Hydrogen burning cycle, the Sun will collapse under its gravitational weight - after one last bright moment as a red giant - and fizzle away as an unremarkable dim object known as a white dwarf (now it's getting really personal).
Think of the Sun as a hot soup of plasma, a fluid of electrically charged atoms and particles. It's turbulent and in perpetual turmoil, as the hot plasma slushes around erratically. The whole ball of fire is also spinning on an axis. When electrically charged particles move, they cast about them a magnetic field. Think of a magnetic field as a network of imaginary lines in empty space emanating from charges in motion. The meaning of such lines is simply this: if other electrically charged particles, like say electrons, wander by a region filled with these line, they will experience a magnetic force. This magnetic force is such that the wandering electrons get channeled along the lines as they spiral around them. So, the space around the Sun is threaded by a beautiful and complex entanglement of such magnetic lines around which charged particles spiral in what can only be described as an elegant and fiery cosmic dance.
But the Sun's plasma is highly turbulent. Occasionally, plasma storms on its surface generate immense eruptions of both plasma and magnetic fields. These can be so violent and energetically packed that the effect propagates all the way to the Earth and hits us in the face (well, technically hits the atmosphere in the face). We can seriously get effected by such solar weather patterns: when eruptions of ions and magnetic fields pass though electronic equipment in satellites or otherwise (that are full of electrons) , bad things can happen. There is also a popular lore of an impending apocalypse driven by a large solar storm… Recently, the Solar Dynamics Observatory captured remarkable close-ups of solar flares. You can check some raw video by clicking here. Or view the accompanying video for more production value but really really corny background music and narrative.