HR: 0830h
AN: SM41A-03    [Abstracts]
TI: Substorm and High Speed Stream Observations During Solar Cyles 22 and 23
AU: * Tanskanen, E I
EM: eija.tanskanen@gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Code 696, Greenbelt, MD 20770 United States
AU: Slavin, J A
AF: NASA Goddard Space Flight Center, Code 696, Greenbelt, MD 20770 United States
AU: Tanskanen, A J
AF: The Whitaker Biomedical Engineering Institute, Johns Hopkins University, Baltimore, MD 21205 United States
AU: Viljanen, A
AF: Finnish Meteorological Institute, Space Research Unit, Helsinki, 00100 Finland
AU: Pulkkinen, T I
AF: Finnish Meteorological Institute, Space Research Unit, Helsinki, 00100 Finland
AU: Koskinen, H E
AF: Finnish Meteorological Institute, Space Research Unit, Helsinki, 00100 Finland
AU: Koskinen, H E
AF: Department of Physics, University of Helsinki, Helsinki, 00014 Finland
AU: Huttunen, K E
AF: Department of Physics, University of Helsinki, Helsinki, 00014 Finland
AB: Magnetic measurements from the MIRACLE network are used to identify substorms during solar cycles 22 and 23, from 1993 to 2004. For the first time substorm activity is examined over a complete solar cycle. In this study more than 5000 substorms are identified and their interplanetary drivers are examined. A new parameter called substorm number R_su is formed based on (monthly) averages of substorm peak amplitudes. The substorm number measures magnetic activity of the Earth's magnetosphere in a way analogous to how sunspot number R_z estimates the level of Sun's magnetic activity. Analysis of WIND, ACE and SOHO interplanetary measurements indicate that high speed streams (HSS, with Sun-to-Earth velocities over 700 km/s) are the main drivers of the terrestrial substorms. The substorm number peaked in 1994-1995 and in 2003-2004 (at 3-4 years after the sunspot maximum), which is when the high speed streams occurred repeatedly every 27 days. During the years of repeated HSSs, substorms occurred more frequently, were more intense, and carried more magnetic energy to the auroral ionosphere, compared to the substorms existing during non-HSS intervals.
DE: 2102 Corotating streams
DE: 2162 Solar cycle variations (7536)
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly