Solar source of the largest geomagnetic storm of cycle 23
Howard, R. A.; Gopalswamy, N.; Michalek, G.; Yashiro, S.; Lepping, R. P.; Xie, H.
United States
Abstract
The largest geomagnetic storm of solar cycle 23 occurred on 2003 November 20 with a Dst index of -472 nT, due to a coronal mass ejection (CME) from active region 0501. The CME near the Sun had a sky-plane speed of ~1660 km/s, but the associated magnetic cloud (MC) arrived with a speed of only 730 km/s. The MC at 1 AU (ACE Observations) had a high magnetic field (~56 nT) and high inclination to the ecliptic plane. The southward component of the MC's magnetic field was made up almost entirely of its axial field because of its east-south-west (ESW) chirality. We suggest that the southward pointing strong axial field of the MC reconnected with Earth's front-side magnetic field, resulting in the largest storm of the solar cycle 23.