Multi‐Band Periodic Poleward‐Moving Auroral Arcs at the Postdawn Sector: A Case Study

• Published in: Journal of geophysical research. Space physics 2023-09, Vol.128 (9), p.n/a
• Main Authors: Yin, Ze‐Fan, Zhou, Xu‐Zhi, Hu, Ze‐Jun, Zong, Qiu‐Gang, Liu, Jian‐Jun, Yue, Chao, Wang, Shan, Zhao, Xing‐Xin, Yang, Hui‐Gen, Li, Bin
• Format: Article
• Language: English
• Subjects: Auroral arcs; Auroras; Boundary layers; dayside aurora; Electron precipitation; Electrons; Elongated structure; Extremely low frequencies; Field line resonance; Ground stations; Instrumentation; Ionosphere; Jupiter; Luminosity; Magnetic fields; Magnetic measurement; Magnetopause; magnetosphere flank region; Magnetospheres; multi‐band auroral observations; Optical measurement; Optical observations; Periodic variations; Perturbation; poleward‐moving auroral arc; Resonance; Rivers; Signatures; ULF waves; ultra‐low frequency wave; Wavelengths
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2023JA031516

Poleward‐moving auroral arcs (PMAAs) with recurrence periods on the order of minutes have been established as a distinct form of auroral activities. Their origin and characteristics, especially those on the dayside, are less understood due to the paucity of observations. Here, we investigate a periodic PMAA event at the postdawn sector based on optical measurements from the high‐latitude Yellow River Station and magnetic measurements from multiple ground‐based stations. The optical observations demonstrate a long duration (∼2.5 hr) of the periodic auroral arcs at not only the well‐established red‐line but also the green‐ and the blue‐lines. This multi‐band feature, together with images at far‐ultraviolet wavelengths, demonstrates a wide energy range of precipitating electrons from hundreds of eV to several keV, with a characteristic energy of ∼2 keV. The auroral luminosity variations at different wavebands show a consistent periodicity within 1.67–3 mHz, which is also shown in the ground‐based magnetic pulsations. The auroral arc and magnetic field observations display signatures of field line resonance, which are likely driven by perturbations at the magnetopause boundary layer. These results complement our knowledge of the dayside periodic PMAAs and improve our understanding of their relationship with ultra‐low frequency waves. Plain Language Summary Aurora is one of the most important phenomena associated with magnetosphere‐ionosphere coupling. Auroral arcs, one of the most prominent auroral forms, are characterized by a narrow width in the north‐south direction but an elongated structure in the east‐west direction. The advanced ground‐based optical instrumentation has demonstrated a distinct type of auroral arcs, the poleward‐moving auroral arcs (PMAAs) with a recurrence period on the order of minutes. However, since stations at relatively‐low latitudes cannot provide optical observations at the dayside due to the sunlit interference, our understanding of periodic PMAAs on the dayside and their associated electron precipitation is very limited. Here, we utilize observations from the high‐latitude Yellow River Station to investigate a periodic PMAA event at the postdawn sector. The optical observations demonstrate the long‐duration characteristics and the multi‐wavelength feature of the periodic arcs. The variations of the auroral luminosity and the ground‐based magnetic field pulsations show consistent periodicity within the ultra‐low frequency (ULF) r