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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
A07S09,
doi:10.1029/2005JA011476,
2006
Major geomagnetic storms (Dst ≤ −100 nT) generated by corotating interaction regions
I. G. Richardson
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Department of Astronomy, University of Maryland, College Park, Maryland, USA
D. F. Webb
Institute for Scientific Research, Boston College, Chestnut Hill, Massachusetts, USA
J. Zhang
School of Computational Sciences, George Mason University, Fairfax, Virginia, USA
D. B. Berdichevsky
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA L-3 Government Services Inc., Chantilly, Virginia, USA
D. A. Biesecker
NOAA Space Environment Center, Boulder, Colorado, USA
J. C. Kasper
Center for Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
R. Kataoka
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
J. T. Steinberg
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
B. J. Thompson
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
C.-C. Wu
NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville, Alabama, USA
A. N. Zhukov
Royal Observatory of Belgium, Brussels, Belgium Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia
Abstract
Seventy-nine major geomagnetic storms (minimum Dst ≤ −100 nT) observed in 1996 to 2004 were the focus of a “Living with a Star” Coordinated Data Analysis Workshop (CDAW) in
March 2005. In nine cases, the storm driver appears to have been purely a corotating interaction region (CIR) without any
contribution from coronal mass ejection-related material (interplanetary coronal mass ejections (ICMEs)). These storms were
generated by structures within CIRs located both before and/or after the stream interface that included persistently southward
magnetic fields for intervals of several hours. We compare their geomagnetic effects with those of 159 CIRs observed during
1996–2005. The major storms form the extreme tail of a continuous distribution of CIR geoeffectiveness which peaks at Dst ∼ −40 nT but is subject to a prominent seasonal variation of ∼40 nT which is ordered by the spring and fall equinoxes and
the solar wind magnetic field direction toward or away from the Sun. The O'Brien and McPherron (2000) equations, which estimate
Dst by integrating the incident solar wind electric field and incorporating a ring current loss term, largely account for the
variation in storm size. They tend to underestimate the size of the larger CIR-associated storms by Dst ∼ 20 nT. This suggests that injection into the ring current may be more efficient than expected in such storms. Four of the
nine major storms in 1996–2004 occurred during a period of less than three solar rotations in September to November 2002,
also the time of maximum mean IMF and solar magnetic field intensity during the current solar cycle. The maximum CIR-storm
strength found in our sample of events, plus additional 23 probable CIR-associated Dst ≤ −100 nT storms in 1972–1995, is (Dst = −161 nT). This is consistent with the maximum storm strength (Dst ∼ −180 nT) expected from the O'Brien and McPherron equations for the typical range of solar wind electric fields associated
with CIRs. This suggests that CIRs alone are unlikely to generate geomagnetic storms that exceed these levels.
Received 17
October
2005;
accepted 21
March
2006;
published 26
May
2006.
Keywords: AL index;
auroral electrojet;
polar cap.
Index Terms: 2102 Interplanetary Physics: Corotating streams; 2134 Interplanetary Physics: Interplanetary magnetic fields; 2164 Interplanetary Physics: Solar wind plasma; 2788 Magnetospheric Physics: Magnetic storms and substorms (7954).
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Citation: Richardson, I. G., et al.
(2006),
Major geomagnetic storms (Dst ≤ −100 nT) generated by corotating interaction regions,
J. Geophys. Res.,
111,
A07S09,
doi:10.1029/2005JA011476.
Copyright 2006 by the American Geophysical Union.
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