Abstract The role of plasma‐sheet bubbles and associated plasma‐sheet bursts, observed as ionospheric flow channels, in the substorm processes is still not fully understood. This study investigates the evolution of auroral activities and meso‐ to small‐scale ionospheric flows during the substorm growth phase, focusing on the influence of auroral streamers and ionospheric flows on the pre‐onset sequence of growth phase arcs and substorm onsets. Utilizing optical data from the THEMIS All‐Sky Imager and radar observations from the Super Dual Auroral Radar Network (SuperDARN), we analyze 56 growth phase arc events and 16 events with flow observations recorded between 2011 and 2016. These events are categorized into four stages: formation, intensification, pseudo‐breakup, and substorm onset. Our observations reveal pre‐onset flow channels reaching the growth phase arc, supporting their importance as precursor sequences leading to substorm onset. Statistical analysis indicates that these flow channels play a critical role in the evolution of growth‐phase arcs and the triggering of substorm onsets. Streamers serve as indicators of the adjacent flow channels. Although streamers may not always be visible all the way to the arc, the associated flows can still be detected. Moreover, most flow channels exhibit azimuthal turning after reaching the growth‐phase arc. Further analysis of flow channel characteristics demonstrates that narrow flow channels commonly involve growth phase arc evolution and substorm onset triggering. In contrast, wide channels mainly contribute to onset triggering. These findings provide new insights into the complex relationship between ionospheric flows and the evolution of auroral structures during substorm development.
Zong et al. (Fri,) studied this question.