Orientation of solar wind dynamic pressure phase fronts

Abstract

Orientation of structures in the solar wind plays an important role when attempting to use upstream observations at L1 for prediction of subsequent conditions near the Earth. In this study, the relationship between solar wind dynamic pressure forcing and geosynchronous magnetic field response is used to determine a very large set of lagged correlations between the ACE and GOES satellites. Effects due to tilted solar wind structures are explored using the dispersion of arrival times relative to a simple phase plane model. Assuming that structure phase-front normal vectors were located in the GSE-xy plane, we found a characteristic azimuth of 15°. Similar analysis carried out with velocity scaling according to the Parker spiral model did not produce an improved fit. Binning by average interplanetary magnetic field (IMF) B→ orientation produced a clear pattern in characteristic azimuth, with phase-front normals perpendicular to both the predominant Parker spiral orientation and the less common ortho-spiral configuration. An empirical relationship φnî=-45°sin(2φB) was found to predict phase-front normal azimuth over the entire range of observed IMF azimuths. The effects of lateral displacement from the Sun-Earth line in the GSE-z direction are comparable to those for GSE-y, indicating that solar wind structures are often significantly inclined with respect to the ecliptic plane. Key PointsSolar wind dynamic pressure and geosynchronous magnetic field correlationPhase front normals perpendicular to Parker spiral and orthospiralEffect of GSE-Y,Z comparable so structures often significantly inclined ©2013. American Geophysical Union. All Rights Reserved.