There are several reasons for geomagnetic variations. The fundamental source is the secular variation in the Earth’s geomagnetic field that slowly occurs in the Earth’s interior within a long-term cycle. The difference of solar wind pressure between the Earth's day side and night side causes daily variation. Geomagnetic storms are the main cause of rapid changes in the geomagnetic field.
Geomagnetic variations caused by changes in space weather conditions are classified in the following way. Such geomagnetic variations create an inflow into the Earth of highly energetic charged particles, which normally are blocked by the geomagnetic field. Thus they create considerable damage to society and the economy because they often directly cause malfunctions in satellites, communications and power transmission facilities.
Event Event Classification Features Duration Geomagnetic Storm (SSC) Begins with rapid increase in H component (SSC), recovers after the remarkable decrease. One to
Sudden Inpulse (SI) Begins with rapid increase in H component (SSC), but no geomagnetic storm occurs. Several
Solar Flare Effect (SFE) Geomagnetic fluctuation by solar flare. Several
Bay Increase in magnetic field during midnight. One hour
SSC Example of each case of geomagnetic variation
SI Example of each case of geomagnetic variation
SFE Example of each case of geomagnetic variation
Bay Example of each case of geomagnetic variation