Solar wind correlations: Statistical and case studies

Abstract

Recent work on solar wind plasma correlations using data from several widely-separated spacecraft (IMP 8, INTERBALL-I, WIND, and ISEE-3) has shown that, for 6-hour periods, the average plasma correlation is 0.7. The focus of these studies has been directed toward a statistical understanding of gross solar wind correlation behavior. In all correlations examined, lower average correlations are caused by the presence of many points from the low correlation subpopulation; nevertheless, data points from the high correlation population are still present. No single organizational factor has yet been found which adequately separates low-correlation periods from high-correlation periods. Some of the spread in correlations is due to the spatial orientations and dimensions of solar wind structures, and thus to the locatiohal alignments of the spacecraft being correlated, but this does not adequately explain all the good or poor correlations since sometimes three nearby spacecraft show poor correlations, while sometimes three widely-separated spacecraft show good correlations. Thus, in order to understand the underlying physics, detailed investigation of individual cases has been undertaken. These results will be important in assigning quality measures to space weather predictions using satellite measurements taken at L1, for example