Fig. 3: The observed Poynting flux in the magnetosphere associated with the auroral arc.
From: Evidence for Alfvén waves powering auroral arc via a static electric potential drop
a The encounter of RBSP-A and -B with the auroral arc during its azimuthal development in magnetic local time. b The frequency spectrogram of the magnetic field using the Morlet wavelet transform for RBSP-A. c The 3D wave Poynting flux (filtered from 0.6 mHz to 100 mHz) in a field-aligned coordinate (FAC) system, where the first component is along the background magnetic field (obtained by a running average over a 20 min window), the second component is along the azimuthally westward direction, and the third component completes the triad system (positive in the outward sense). d, e are for RBSP-B, in the same format as (b, c). Higher cadence Poynting flux (0.6 mHz to 4 Hz) is available at RBSP-B, showing a peak value around 350 mW/m2. For each satellite, the vertical dotted lines in (c, e) mark the 2 minutes right after the dipolarization time in a. Detailed spectral information within the 2 minutes for the Poynting flux and E/B ratio are presented in the Fig. 5.
