Geomagnetic signatures during the intense geomagnetic storms of 29 October and 20 November 2003

Solar cycle 23 in its declining phase witnessed the most pronounced space weather events during October–November 2003. A series of powerful solar flares and associated geoeffective Coronal Mass Ejections (CMEs) travelling at ∼2000 km/s drove shock fronts that impacted the Earth's magnetic field consecutively on 29 and 30 October, resulting in intense geomagnetic disturbances during 29–31 October. Another intense geomagnetic storm activity occurred during 20–21 November, resulting from a solar flare that had an associated geoeffective CME travelling at a speed of ∼1100 km/s. Digital ground magnetic field measurements from the equatorial and low-latitude locations in the Indian longitude zone, in conjuction with the interplanetary solar wind and magnetic filed parameters, are used to study the characteristics of these storms. Maximum magnitude of the total magnetospheric energy injected into the magnetosphere during the mainphase of the three major storm amounts to approximately 4.5×1013, 3.6×1013, 2.8×1013 W. Another salient feature brought out is the close correspondence between the magnitude of the peak of the southward component of the interplanetary magnetic field Bz and the strength of the storm intensity as inferred from the Dst and low-latitude digital magnetic records.