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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L12S09, doi:10.1029/2004GL021639, 2005

Solar source of the largest geomagnetic storm of cycle 23

N. Gopalswamy

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


S. Yashiro

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


G. Michalek

Physics Department, Catholic University of America, Washington, D. C., USA


H. Xie

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


R. P. Lepping

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


R. A. Howard

Naval Research Laboratory, Washington, D. C., USA


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.

Received 29 September 2004; accepted 28 December 2004; published 13 May 2005.

Index Terms: 2111 Interplanetary Physics: Ejecta, driver gases, and magnetic clouds; 2139 Interplanetary Physics: Interplanetary shocks; 2164 Interplanetary Physics: Solar wind plasma; 2788 Magnetospheric Physics: Magnetic storms and substorms (7954); 7513 Solar Physics, Astrophysics, and Astronomy: Coronal mass ejections (2101).

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Citation: Gopalswamy, N., S. Yashiro, G. Michalek, H. Xie, R. P. Lepping, and R. A. Howard (2005), Solar source of the largest geomagnetic storm of cycle 23, Geophys. Res. Lett., 32, L12S09, doi:10.1029/2004GL021639.