Fig. 4. EBWs observed near EDR.

a B. b Perpendicular and parallel components of the high-frequency E with $f>$50 Hz. (c) E$\times$B/B${}^2$ (lines) and 30-ms resolution V${}_{\mathrm{e},\perp }$ (dots). d Power spectrogram of E${}_{\perp }$. e Power spectrogram of B. The electron cyclotron harmonic frequencies are plotted in (d, e). The yellow-shaded region from 15:03:32.037 to 15:03:32.054 UTC highlights the E fluctuations with amplitudes larger than E${}_{\mathrm{peak}}$/$e^2$, where E${}_{\mathrm{peak}}$ is the peak of the fluctuating E, and e $~2.718$ is the Euler identity. f Power spectrum of E${}_{\perp }$ within the yellow-shaded region. The average $f_{\mathrm{ce}}$ and the harmonic frequencies are over-plotted. g, h Hodograms of E${}_{\max }$ versus E${}_{\mathrm{int}}$, and E${}_{\max }$ versus E${}_{\min }$. The red line in (h) denotes the B direction. During the EBWs observations, the electron plasma frequency $f_{\mathrm{pe}}~$ 32.9 kHz is well above the electron cyclotron frequency $f_{\mathrm{ce}}~$ 860 Hz.