| Summary: | The Energetic particles are released from the Sun by solar flares or eruptive ejections interaction with geomagnetic field producing geomagnetic storms and more ionization in the ionosphere. The geomagnetic substorms are classified as one of major factor that influence geomagnetically induced currents (GIC) that affect the operation of technological system through the geomagnetic field variations. The direct representation of GIC is the time derivative of the horizontal geomagnetic field. 138 substorms onset events were obtained from IMAGE magnetometer data from Northern Europe, using Dst (Disturbance storm time) to determine the substorm events of varying strengths, for five stations (Addis Ababa, Abisko, Bangui Hermanus and Nurmijarvi). The data used in this study covers the periods from 1999 to 2001. Positive high correlation exhibited between the maximum value of time derivatives of the horizontal geomagnetic field (dH/dtmax) and maximum value of horizontal geomagnetic field (max H). Also, Monthly variations of the maximum value of time derivatives of the horizontal geomagnetic field (dH/dtmax) and maximum value of the horizontal geomagnetic field (max H) were also investigated.
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