 Some openings are caused by islands of intense ionization of the upper atmosphere known as the E Layer ionosphere.These islands of intense ionization are called "Sporadic E" and result in erratic but often strong propagation characteristics on the "low band" VHF radio frequencies.The 6 meter amateur band falls into this category, often called "The Magic Band", 6 meters will often "open up" from one small area into another small geographic area 1000–1700 km away during the spring and early summer months.