Physical Science International Journal

This study focuses on the dynamics of the subsolar position ( , in Earth radii ) of the magnetopause in response to events originating in corotating interaction regions (CIRs) during the declining phase of solar cycle 24. Based on analyses using the models developed by Shue et al. (1998), Liu et al. (2015) and Lin et al. (2010), we quantify the impact of mechanical and electromagnetic couplings on this boundary. We analyse these dynamics based on the north–south component of the interplanetary magnetic field ( B_z, in nT ), the total interplanetary magnetic field strength ( B, in nT ), the dynamic pressure of the solar wind (P_d, in nPa ), and the magnetic pressure (P_m, in nPa ). Additionally, we consider the normalised solar wind–magnetosphere coupling index (N), derived from the Newell et al. (2007) function and scaled by a normalisation factor of 10⁻⁴. Analysis of the temporal profiles across the different phases of the CIR storms studied reveals progressive and oscillatory variations in the magnetopause's subsolar position (R_o ). Our results reveal significant compressions, with a reduction in R_o amplitude ranging from 0.9 R_e  to 5 R_e . The main minimum R_o  reached during these CIR events studied is 6.4 R_e , pushing the magnetopause below the geosynchronous orbit (6.6 R_e ). The originality of this study lies in the joint application of cross-correlation, Granger causality, and Bootstrap, an approach that allows dissociating the information-contribution delay (Granger causality) from the time required for the maximum physical adjustment of R_o  to the various constraints imposed by solar drivers. Granger causality analysis reveals that predictability is not always immediate: while it is instantaneous for certain drivers, it takes between 14 and 21 minutes for past values of  to P_d improve the prediction of R_o during the CIR event of 27 March 2017, and 18 to 20 minutes for the intensity of the interplanetary magnetic field B in the event of 20 January 2016. Regarding physical adjustment, while the responses to  and the coupling index (N) are immediate across all six events, the analysis reveals remarkable inertia in the other parameters. The adjustment to the B_z constraint took 33 min to reach its maximum during a specific event. In the six CIR events studied, the adjustment of R_o to the IMF B intensity constraint was slow, with delays ranging from 10 minutes to more than 2 hours (8 min to 130 min). These prolonged delays, particularly well captured by the Lin and Liu models, indicate a hysteresis effect and a slow, global reconfiguration of magnetospheric currents.