Fig. 7. Two-dimensional (2D) slice from 3D electron distribution functions.

a Electron distribution functions with electron kinetic velocity of 8.6$\times 10^3$ km s${}^{-1}$ (corresponding to 212 eV). The green, magenta, and red arrowed lines denote the directions of V_E, V_B, and V_E×B, respectively. The black circle represents the V_E − V_E×B plane perpendicular to the magnetic field B, and the two dashed circles show the ranges of $\pm 22.5^{\circ }$ away from the V_E − V_E×B plane. The blue arrowed line labeled as E${}_{\mathrm{EBW}}$, show the E${}_{\max }$ direction of the EBWs. The white dot in panel (a) and the white square in panel (b) highlight the location with the largest phase-space density of the electron crescent. The intense phase-space densities close to the V_B direction corresponds to the parallel magnetosheath electrons moving towards the X line (see Fig. 3f). b 2D slice of the distribution function on the V_E − V_E×B plane is from the average phase-space densities within $\pm 22.5^{\circ }$ from the perpendicular plane. The black circle denotes the electron velocity of 8.6$\times 10^3$ km s${}^{-1}$. The black and blue lines show the projected directions with the peak phase-space density of the electron crescents and the E${}_{\max }$ direction, respectively.