Space Weather Conditions Associated with Highly Perturbed Interplanetary Conditions and the Heliospheric Relaxation Phase During Solar Cycle 24

Abstract

Space weather conditions are strongly influenced by variations in interplanetary parameters and Solar Cycle (SC) dynamics. SC 24 exhibited distinct phases of heliospheric relaxation and highly perturbed interplanetary conditions, providing a unique framework for analysis. Understanding these contrasting phases is essential for evaluating factors associated with geomagnetic activity and their impact on the near-Earth environment. This study aims to examine the relationship between solar activity, interplanetary parameters, and geomagnetic responses, and to identify the primary physical mechanisms governing space weather during this cycle. A dataset (Annual average) covering SC 24 was analysed using solar activity indices (sunspot number and F10.7 flux), interplanetary parameters (IMF magnitude (Scalar B), solar wind speed, plasma temperature, and proton density), and geomagnetic indices (Dst, Kp, Ap, AE, AL, AU). The data were obtained from NGDC/NOAA, and WDC Kyoto. Statistical methods (correlation coefficient, regression analysis) were applied to evaluate parameter relationships Solar activity proxies are strongly correlated with each other (r = 0.67) but exhibit weak correlations with geomagnetic indices. In contrast, interplanetary parameters, particularly IMF strength and solar wind speed, show stronger control over geomagnetic activity. During the deep minimum (2008-2009), IMF (Scalar B) decreased to 3.89 nT and solar wind speed to 360 km s-1, while during the maximum phase, values increased only modestly (Scalar B = 5.71 nT, V = 420 km s-1). The AE index increased significantly from 68 nT to 177 nT, whereas Dst remained relatively weak (-10 to -12 nT), indicating suppressed ring current activity. Additionally, proton density showed negligible correlation with geomagnetic indices despite a strong correlation with the Alfvén Mach number (r = 0.99). The results suggest that coronal mass ejections during SC 24 were associated with propagation through a comparatively low-pressure heliospheric environment, a condition that may have contributed to enhanced expansion and reduced magnetic field strength at 1 AU. This interpretation is consistent with the observed reduction in CME geo-effectiveness during the cycle. Consequently, the relatively low occurrence of intense geomagnetic storms appears to be linked to weakened interplanetary magnetic conditions, while moderate and persistent geomagnetic disturbances were more strongly associated with recurrent corotating interaction regions and high-speed solar wind streams. SC 24 demonstrates a shift in space weather dynamics, where interplanetary conditions dominate over solar activity proxies in controlling geomagnetic responses. These findings highlight the need to incorporate heliospheric background conditions into forecasting models. Future studies should focus on multi-point observations and advanced modelling approaches to improve space weather prediction under low solar activity conditions.