Aurora ripples - a visual ionospheric emissions when auroral plasma sweeping through atmosphere

Based on the multi-scale statistical observations from antarctic Zhongshan station, a rippling aurora-like optical phenomena was observed near the poleward boundary of the aurora. The lack of red emission and extremely small scale indicated the aurora ripple is not likely been the result of the electron or ion perception along the magnetic field line. Through the statistical results of appearance location, fine scale structures and the consistence to the theoretical predication, the Aurora ripple is believed to be mainly caused by the plasma gradient drift instability around aurora. Dreyer et al described this phenomena as Fragmented aurora-like emissions in 2019, considering the patterns of emergence and progression associated with this phenomenon, we suggest to name it as "Aurora ripples". This designation is inspired by the visual resemblance of the phenomenon to rippless formed when a paddle moves through a lake, signifying the interaction of auroral plasma with the atmosphere.