Comparative statistical analysis of storm time activations and sawtooth events

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Read Full Article (file size: 1123419 bytes) Cited by 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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