Solar storms are a variety of eruptions of mass and energy from the solar surface.
Flares, prominences, sunspots, coronal mass ejections are the common harbingers of solar activity, as are plages and other related phenomena seen at other wavelengths. They all involve sudden releases of stored magnetic energy, which accelerates the hot gases near the surface or in the corona of the Sun. Sometimes these particles make it all the way to the Earth and beyond by flowing along the Sun's magnetic field into interplanetary space. When the material collides with the Earth's magnetic field and trapped radiation belts, it can dump particles into our upper atmosphere to cause the Aurora. The same 'charged' particles can produce their own magnetic fields which can modify the Earth's magnetic field and affect compass readings.