Evidence for Presence of a Global Resonant Mode of Oscillations During High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events

The interaction between the Sun and the Earth defines the space environment of the Earth. This interaction is complex and exhibits various time scales ranging from a  few seconds to years. The High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events are mainly the manifestations of the interactions of the corotating interaction regions (CIRs) with the terrestrial magnetosphere which continues for several days. The responses of two HILDCAA events are investigated by using solar wind observations at the L1 point, magnetospheric measurements at geosynchronous orbit, and changes in the global ionosphere. This study provides evidence of the existence of quasi-periodic oscillations (1.5-2hr) in the ionospheric electric field over low latitude, total electron content at high latitude, the magnetic field over the globe, energetic electron flux and magnetic field at geosynchronous orbit, geomagnetic indices (SYM-H, AE, and PC) and the Y-component of the interplanetary electric field (IEFy) during the HILDCAA events at all local times. Based on detailed wavelet and cross-spectrum analyses, it is shown that the periodic oscillations of 1.5-2hr in IEFy are the most effective one that controls the solar wind-magnetosphere-ionosphere coupling process during the  HILDCAA events for several days. Therefore, this investigation for the first time, shows that the  HILDCAA event affects the global magnetosphere-ionosphere system with a “resonant” mode of oscillation. These results are important not only to evaluate the solar wind-magnetosphere-ionosphere coupling process during the HILDCAA events but can also help to build up a forecasting strategy in the future.