Geomagnetic storm

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About geomagnetic storm-

• A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth’s magnetosphere caused by a solar wind shock wave and/or cloud of magnetic field that interacts with the Earth’s magnetic field.
• Such solar “storms” are caused by powerful explosions on the sun’s surface, which spit out plasma and magnetic fields that can hit the Earth.
• A geomagnetic storm occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. 
• These storms result from variations in the solar wind that produce major changes in the currents, plasmas, and fields in Earth’s magnetosphere. 
• The solar wind conditions that are effective for creating geomagnetic storms are sustained periods of high-speed solar wind, and most importantly, a southward directed solar wind magnetic field (opposite the direction of Earth’s field) at the dayside of the magnetosphere. 
• The largest storms that result from these conditions are associated with solar coronal mass ejections (CMEs) where a billion tons or so of plasma from the sun, with its embedded magnetic field, arrives at Earth. 
• Another solar wind disturbance that creates conditions favorable to geomagnetic storms is a high-speed solar wind stream (HSS). 
• HSSs plow into the slower solar wind in front and create co-rotating interaction regions, or CIRs. 
• These regions are often related to geomagnetic storms that while less intense than CME storms, often can deposit more energy in Earth’s magnetosphere over a longer interval.
• Storms also result in intense currents in the magnetosphere, changes in the radiation belts, and changes in the ionosphere, including heating the ionosphere and upper atmosphere region called the thermosphere. 
• A measure of this current, the disturbance storm time (Dst) index, has been used historically to characterize the size of a geomagnetic storm. 
• In addition, there are currents produced in the magnetosphere that follow the magnetic field, called field-aligned currents, and these connect to intense currents in the auroral ionosphere. 
• These auroral currents, called the auroral electrojets, also produce large magnetic disturbances. 
• While the storms create beautiful aurora, they also can disrupt navigation systems such as the Global Navigation Satellite System (GNSS) and create harmful geomagnetic induced currents (GICs) in the power grid and pipelines.

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