Solar wind parameters' behavior before and after magnetic storms

Search for geoeffective solar wind parameters is a key for successful building of magnetic storm prognosis. So, it is important to know which solar wind structures are mainly geoeffective for whole body of magnetic storms and which typical conditions in solar wind precede magnetic storms with Dst < -30 nT. We used the list of storm main phase onsets for 1976-2000 and list of magnetic storms with sudden commencements (SSC only) for 1963-2003. Comparison of pre-and after-onset distributions of solar wind parameters with whole-data distributions shows that solar wind behavior before and after the onsets of all magnetic storms is different from the well-known behavior of the solar wind before and after severe magnetic storms: density plays more significant geoeffective role than velocity. Some pre- and after-storm solar wind features are different from the statistical average of solar wind conditions. (C) 2007 Elsevier Ltd. All rights reserved.