Figure 2

Relative efficiency of recent 10 year’s Sun-Earth coupling compared to previous 40 years. Ratio of Dst, Kp, and AL values during the most recent 10 years (2005 −2014) to the average of the previous four decades (10-year averages are further averaged) are plotted against various solar wind input parameters: (a) modified Akasofu’s \(\epsilon ' = (4\pi /\mu _{0})\cdot \textit {V}_{\textit {SW}}\cdot \textit {B}_{\text {tan}}^{2}\cdot \textit {sin}^{4}(\theta _{c}/2\)), (b) Newell’s flux accumulation rate \(d\Phi /dt = (V_{\textit {SW}}^{2}\cdot \textit {B}_{\text {tan}}\cdot \textit {sin}^{4}(\theta _{c}/2))^{2/3}\), (c) solar wind proton density N _P , (d) solar wind dynamic pressure P _SW , (e) solar wind electric field E _Y , and (f) product of d Φ/d t and F10.7 index. The approximate error range (several %) that includes both statistical error and the differences between each decade before 2005 is indicated by green hatch. Linear scales are used for P _SW , E _Y , and N _P while logarithmic scales are used for ε ^′ and d Φ/d t.