An aurora is most likely to occur during periods of high solar activity when there is a high probability of a large solar flare. When such an eruption occurs, charged particles from the flare may spiral towards earth arriving about a day later. This may or may not cause an aurora: if the interstellar magnetic field has same polarity, the particles do not get coupled to the geomagnetic field efficiently. Besides sunspot-related active solar surface areas, other solar phenomena that produce particles causing auroras, such as re-occurring coronal holes spraying out intense solar wind. These charged particles are affected and captured by the geomagnetic field and the various radiation belts surrounding earth. The aurora-producing relativistic electrons eventually precipitate towards earth's magnetic poles, resulting in an aurora which disrupts short-wave communications (SID) due to ionospheric/magnetic storms in the D, E, and F layers. Various visual effects are also seen in the sky towards the north – aptly called the Northern Lights. The same effect occurs in the Southern Hemisphere, but the visual effects are towards the south. The auroral event starts by onset of geomagnetic storm, followed by number of sub-storms over the next day or so.