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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
A01205,
doi:10.1029/2006JA012024,
2007
Comparative statistical analysis of storm time activations and sawtooth events
T. I. Pulkkinen
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
N. Partamies
Institute for Space Research, University of Calgary, Calgary, Alberta, Canada
R. L. McPherron
Institute for Geophysics and Planetary Physics, University of California, Los Angeles, California, USA
M. Henderson
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
G. D. Reeves
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
M. F. Thomsen
Los Alamos National Laboratory, Los Alamos, New Mexico, USA
H. J. Singer
Space Environment Center, Boulder, Colorado, USA
Abstract
Statistical properties of storm time magnetospheric activity are examined using superposed epoch analysis. We show that about
half of storm time auroral electrojet activations have signatures that are typical of nonstorm substorms, including geostationary
orbit injections and magnetic field dipolarizations. Analysis of a separate data set of sawtooth events shows that they have
auroral and inner magnetosphere characteristics that are quite similar to those found generally during storm time activity.
Hence it is concluded that the sawtooth events do not represent a specific class of magnetospheric activity. Examination of
the solar wind and IMF properties showed that about 30% of storm time substorm-like activations and about 20% of the sawtooth
oscillations have associated solar wind or IMF triggers and that triggering is more likely during high solar wind pressure
and fluctuating IMF. The solar wind-magnetosphere coupling efficiency is shown to be independent of the solar wind Mach number
or level of IMF fluctuations but dependent on the level of driving; when E Y is small, the ionospheric dissipation, ring current intensification, and geostationary field stretching are relatively larger
than when the driving E Y is large.
Received 15
August
2006;
accepted 25
October
2006;
published 11
January
2007.
Keywords: global MHD simulations;
magnetospheric energetics;
substorms.
Index Terms: 2788 Magnetospheric Physics: Magnetic storms and substorms (7954); 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics; 2720 Magnetospheric Physics: Energetic particles: trapped; 2753 Magnetospheric Physics: Numerical modeling.
Read Full Article (file size: 1123419 bytes) Cited by
Citation: Pulkkinen, T. I., N. Partamies, R. L. McPherron, M. Henderson, G. D. Reeves, M. F. Thomsen, and H. J. Singer
(2007),
Comparative statistical analysis of storm time activations and sawtooth events,
J. Geophys. Res.,
112,
A01205,
doi:10.1029/2006JA012024.
Copyright 2007 by the American Geophysical Union.
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