Response of the geomagnetic activity to solar wind turbulence during solar cycle 23

The solar wind-magnetosphere coupled system is characterized by dynamical processes. Recent works have shown that nonlinear couplings and turbulence might play a key role in the study of solar wind-magnetosphere interaction processes. Within this framework, this study presents a statistical analysis aimed to investigate the relationship between solar wind MHD turbulence and geomagnetic activity at high and low latitudes as measured by the AE and SYM-H indices, respectively. This analysis has been performed for different phases of solar cycle 23. The state of turbulence was characterized by means of 2-D histograms of the normalized cross-helicity and the normalized residual energy. The geomagnetic response was then studied in relation to those histograms. The results found clearly show that, from a statistical point of view, solar cycle 23 is somewhat peculiar. Indeed, good Alfvenic correlations are found unexpectedly even during solar activity maximum. This fact has implications on the geomagnetic response as well since a statistical relationship is found between Alfvenic fluctuations and auroral activity. Conversely, solar wind turbulence does not seem to play a relevant role in the geomagnetic response at low latitudes. (C) 2011 Elsevier Ltd. All rights reserved.