On density and pressure variations in the solar wind plasma

Abstract: A study of ACE solar wind data at lAU, for the period from 1998 to early 2005, was conducted. This was done in order to find sudden solar wind pressure enhancements accounting for plasma transfer through the magnetopause. In order to get information about the extent and orientation of the structures found, a correlation of found events to data from the Wind satellite was done. The enhancements considered are those with a relative increase exceeding unity. These are found by applying a 1-hour box-car average to the data set. A part of the event distribution was found to vary at periodicities of 11 years, 140 days, and 29 days. Most of the pressure enhancements found were due to a corresponding increase in plasma density. The transverse extent of most of the structures found was rather large, i.e., of the order of 100 Earth radii and the mean orientation of the plasma fronts  were found  to lie between the radial direction and that of  the Archimedean spiral. The duration of most of the structures was shorter than 1 hour. An investigation of the direction of the GSE Z-component of the magnetic field of the events, showed that there was no predominant orientation.