Journal Article

Special Particle Precipitation Signatures Over Giant Auroral Undulations During the 7 September 2015 Geomagnetic Storm

Zhang, Yong‐Liang, Rong, Zhaojin, Yao, Zhong‐Hua, Liu, Libo, Wei, Yong, Zhang, Xiao‐Xin, Zhou, Yi‐Jia, He, Fei

2024

Overview

Giant undulations (GUs) have been well established to be the optical manifestation of the plasmapause surface wave (PSW) where the wave‐particle interactions provide particle sources to generate auroras. However, their detailed particles precipitation signatures in the ionosphere remain unclear. Here we analyze multi‐satellite conjugated observations in the ionosphere during a prominent GUs event, revealing the two‐zone precipitation pattern including energetic proton precipitations responsible for the main body of GUs and low‐energy electron precipitations for the edge of GUs. Interestingly, the occurrence of GUs is also accompanied with high‐energy particles precipitations of hundreds of keV and magnetic disturbances of three components. The sizes of sawtooth in the GUs correlate positively with the strength of adjacent subauroral polarization streams (SAPS). The two‐zone precipitation pattern and high‐energy particles precipitation over GUs are potentially related to the plasma sheet and very‐low frequency wave (VLF) modulation of the PSW, respectively. Plain Language Summary Planetary boundaries are mostly disturbed and dynamic, thus controlling energy, mass and momentum transfers for the whole active system. As a typical form of boundary dynamics, the surface wave inherently developed near the boundary when undergoing perturbation. For the earth, they are magnetopause surface wave on the magnetopause and plasmapause surface wave near the plasmapause from outer to inner region. Generally, the observation of surface wave is rare mostly due to sporadic magnetospheric probes. Recently, a series of works have confirmed the ionospheric giant undulations being the optical manifestation of plasmapause surface wave. Even though the close correlation between them, the important intermediate physical processes, including wave‐particle interaction, particle precipitation, ionospheric signatures, is hardly explored and thus unknown. Therefore, we have prudently shown the signatures of particles precipitation and magnetic field disturbance above giant undulations, and the close relation between the sizes of giant undulations and the velocities of their equatorward subauroral polarization streams. Our results would help to reveal the crucial middle processes between the originating plasmapause surface wave and resulting giant undulations, and to remotely monitor the boundary dynamics with higher temporal‐spatial resolution. Key Points The main body of GUs is lighted by energetic proton precipitation while the edge is lighted by low‐energy electron precipitation Occurrence of GUs is accompanied with particle precipitations of hundreds of keV and magnetic field three components perturbations It is suggested that the size of sawtooth correlates positively to their equatorward SAPS/SAID strength

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Active control / Auroras / Creeks & streams / Earth magnetosphere / Energy / Geomagnetic storms / Ionosphere / Magnetic disturbances / Magnetic field / Magnetic fields / Magnetic storms / Magnetopause / Momentum / Particle interactions / Particle physics / Particle precipitation / Pattern analysis / Plasmapause / Polarization / Precipitation / Precipitation patterns / Remote monitoring / Rivers / Satellite observation / Signatures / Spatial discrimination / Spatial resolution / Storms / Surface water waves / Surface waves / Very Low Frequencies