Variation of the H Component of Geomagnetic Field: Relationship to the Ring and Field Aligned Currents

Disturbance of equatorial ring current during the geomagnetic storm has dominant effect on geomagnetic field. The short term irregular variation on geomagnetic field is characterized by interaction of solar-wind magnetic field and Earth’s magnetosphere, which develops time varying current in magnetosphere and ionosphere. This study represents the irregular variation on H component of Earth’s magnetic field during three intense geomagnetic storm events. Among the five selected stations, four are at low-latitude and remaining one is at middle latitude. All the stations recorded the maximum depression on H component during the main phase of storm but sudden storm commencements (SSCs) event before initial phase caused slight increase in magnitude. In each of the event, low-latitude stations recorded large perturbation on magnetic field as compared to the middle latitude station. This result supports the intensification of ring current as initiated by the transfer of plasma and energy through interplanetary coronal mass ejections (ICMEs) and finally causes falling off of H component. Kakadu station (southern latitude) showed maximum value of ΔH in second and third event, this result keeps up that mostly southern hemisphere station measures large decline on H component during storm time. The calculated value of ring current and field aligned current (FAC) showed extreme negative correlation with ΔH. This unique result reveals that ring current is not only a factor that cause disturbance on horizontal component of Earth’s magnetic field but FAC also has considerable effect.