Invariability of relationships between the solar wind electric field EKL and the magnetic activity indices PC, AL and Dst

Abstract

The daily values of the EKL field and indices of magnetic activity PC, AL and Dst were used to verify stability of relationships between these parameters in course of 23rd and 24th solar cycles. The results of analysis demonstrate that the mean level of correlation between the EKL field and PC index remains in range R = 0.85–0.90 over 24 years. During the solar maximum epochs (2008, 2015) the correlation between EKL and PC reduced down to R = 0.75, the decrease being related to solar protons events (SPE), which strongly affect the ionospheric conductivity in polar caps. In the course of both cycles the daily AL index well correlated with PC index (R = 0.93) and with EKL field (R = 0.83); correlation of daily Dst index with PC and EKL values was much worse (R = 0.72 and 0.64, correspondingly), the correlation being independent of solar activity epochs and cycles. The PC indices in northern (PCN) and southern (PCS) indices hemispheres demonstrate the evident seasonal variation; the PCsummer index is commonly larger than the PCwinter index, but PCwinter index better correlates with EKL field. The conclusion is made that relationships between the EKL field, PC index, and the magnetic disturbance indices AL and Dst remained valid in course of 23rd and 24th solar cycles and, therefore, the calibrating coefficients, determining these relationships, are not affected by solar activity.