Small-Scale Dynamic Aurora
Ryuho Kataoka, C. C. Chaston, D. J. Knudsen, K. A. Lynch, R. L. Lysak, Yan Song, R. Rankin, Kiyoka Murase, Takeshi Sakanoi, J. L. Semeter, Tomo-Hiko Watanabe, Daniel Whiter
Abstract
Small-scale dynamic auroras have spatial scales of a few km or less, and temporal scales of a few seconds or less, which visualize the complex interplay among charged particles, Alfvén waves, and plasma instabilities working in the magnetosphere-ionosphere coupled regions. We summarize the observed properties of flickering auroras, vortex motions, and filamentary structures. We also summarize the development of fundamental theories, such as dispersive Alfvén waves (DAWs), plasma instabilities in the auroral acceleration region, ionospheric feedback instabilities (IFI), and the ionospheric Alfvén resonator (IAR). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11214-021-00796-w.