Of its many dynamic features, perhaps the most important and basic is the so-called magnetospheric substorm , a period of the order of one hour or less, during which energy is rapidly released in the magnetospheric tail. During substorms, in the polar regions, aurora becomes widespread and intense, also much more agitated, and the Earth's magnetic field is disturbed. Out in space, ions and electrons flow in much greater numbers and at higher energies, and changes in the magnetic field are much more profound than those seen at Earth. These decreases in the magnetic field are world-wide and are readily observed at any place. Typically, a storm takes about half a day to develop, and it gradually decays over the next few days.
Magnetic storms are relatively rare.
They are also much more frequent, often just hours apart. The two are of course related, and during magnetic storms intense substorms are generally observed in the polar regions. Substorms usually do not inject as many particles. Substorms at Earth and in Space On Earth the most visible sign of a substorm is a great increase of polar auroras in the midnight auroral zone. Their activity may build up for half an hour and then decay, but as with atmospheric weather, patterns are quite variable.