Fragmented Aurora-Like Emissions-a Visualization of Aurora Aroused Ionospheric Instability Ripples

A unique rippling luminous structure near the main aurora, lacking a red glow and smaller in scale, has been documented. These ripples are not caused by electron or ion precipitation along geomagnetic field lines. We have characterized these Fragmented Aurora-like Emissions (FAEs) through statistical analysis, revealing that they appear as green, periodic structures near the poleward edge of a strong aurora arc, especially when the arc retreats from higher latitudes. Moreover, FAEs tend to appear earlier when the aurora arc retreats more rapidly from its maximum expansion. The distances between the ripples range from 4 to 5 km. We present new evidence supporting the hypothesis that FAEs are caused by plasma gradient drift instability ripples occurring near the aurora ionosphere. This research expands our understanding of aurora dynamics and the physical processes in aurora regions; FAEs can be regarded as a signal of the environment around aurora reach to the gradient drift instability favorable conditions.