Intermittent Lobe Reconnection Under Prolonged Northward Interplanetary Magnetic Field Condition: Insights From Cusp Spot Event Observations

Previous studies have suggested that lobe reconnection under stable northward interplanetary magnetic field (IMF) conditions should be continuous. However, to what extent it can be considered as continuous is unknown. Auroral cusp spots have been considered a signature of lobe reconnection. Here, we show that during a cusp spot event continuously observed by the Defense Meteorological Satellite Program for approximately 4 hr under stable IMF conditions, the ground radars recorded multiple intermittent equatorward-moving radar forms (EMRFs) near local noon and multiple intermittent poleward-moving radar forms (PMRFs) at post-noon, each lasting similar to 20-30 min. These intermittent EMRFs and PMRFs are suggested to correspond to intermittent lobe reconnections occurring at the cusp's poleward boundary near local noon and the duskside boundary at post-noon, respectively. These findings challenge the previously held notion of continuous lobe reconnection under stable IMF conditions. Under certain conditions where the solar wind magnetic field points toward the North, there is a higher chance of a specific type of magnetic interaction called "lobe reconnection" happening near the Earth's dayside boundary with space. Previous findings suggested that lobe reconnection could occur continuously under stable interplanetary magnetic field conditions. Based on coordinated satellite and ground observations of auroral cusp spot event, we revealed that the pattern of lobe reconnection is intermittent rather than continuous. This discovery holds particular significance in advancing our understanding of the solar wind-magnetosphere coupling process in the cusp region. A continuous auroral cusp spot is confirmed to be in conjunction with repeated equatorward or poleward-moving radar forms (PMRFs)Each equatorward or PMRF is suggested to correspond to an isolated lobe reconnectionThe lobe reconnection is suggested to be intermittent, rather than continuous, even under stable interplanetary magnetic field conditions