[P-EM15] Dynamics of Magnetosphere and Ionosphere

[PEM15-05] Multiscale Dynamics of Inertial Alfvén Waves and the Coupled Electron-Proton Energization in the Auroral Ionosphere

*Francesca Di Mare^1,2 (1.NASA Goddard Space Flight Center, Greenbelt, Maryland, USA、2.The Catholic University of America, Washington, DC, USA)

キーワード：multiscale energy cascade, turbulence, ionosphere, Alfvén waves, kinetic dampings, sounding rocket measurements

We report observations of a novel regime of inertial Alfvén wave (IAW) turbulence in the very low beta plasma of the auroral ionosphere. Using data from The Twin Rockets to Investigate Cusp Electrodynamics (TRICE-2) mission, we analyze turbulent electric and magnetic fields, and their frequency spectra, to characterize the nature of the turbulence. We observe a multiscale turbulent cascade, distinct from those seen in other space plasmas such as the solar wind and solar corona. This cascade extends to significantly smaller scales than typically observed, impacting both electron and proton energization. The unique conditions of the auroral ionosphere, particularly the strong magnetic field, lead to significant electron inertia effects. These effects modify the wave properties of the IAWs, causing them to propagate with phase speeds exceeding the electron thermal speed. Our findings suggest that the resulting IAW turbulence not only energizes electrons via Landau damping (a process recently directly observed in space plasmas) but also facilitates proton energization through cyclotron damping. This latter process, involving resonant interactions between protons and the IAWs, has not been previously well-characterized in this environment. These TRICE-2 observations provide compelling evidence for this previously unrecognized mechanism of proton energization in the ionosphere during disturbed space weather conditions, highlighting the crucial role of the observed multiscale cascade of IAW turbulence in driving plasma dynamics and energy transfer in this region.