Geomagnetic storms are major disturbances or fluctuation of the magnetosphere that happen when the interplanetary magnetic field turns southward and is constantly staying southward for an extremely long period of time. They are also associated with solar flares, solar wind, or sunspot. Geomagnetic storms can be known as recurrent or non-recurrent storms depending on some different characteristics. They are caused by pole unsteadiness in the Earth's crustal plates. There are different phases of geomagnetic storms, and also three didn’t types of these storms.
There are three main types of geomagnetic storms: minor, major, and severe. Minor geomagnetic storms are storms in which the Ap index is greater than twenty-nine, but is less than fifty. A major geomagnetic storm is a storm in which the Ap index is greater than forty-nine, but is less than one hundred. The final type of geomagnetic storm, severe, is a storm in which the Ap index is greater than one hundred. Ap index is the planetary index for measuring the strength of disturbance in the Earth's magnetic field. Not only are there different types of geomagnetic storms, but throughout the storms there are multiple different phases.
During the one of the phases, main phase, which is the next phase of the storms, is when the horizontal magnetic field at middle latitudes is starting to decrease at a consistent rate. This phase usually lasts from two to two and a half days if there is a severe geomagnetic storm. Charged particles in the close to earth plasma sheet are energized and injected deeper into the inner magnetosphere. It produces the storm-time ring current. The main phase is characterized by the occurrence of many intense sub storms. When the interplanetary field turns toward the north again, the rate of plasma energization and inward transport slows and the variety of loss processes that remove plasma from the ring current begin to restore it to its pre-storm state. An increase in...
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