Figure 3

Dispersion curves of the wave and the cross-field electron flux. (a) The PSD mappings (colored scale) of the \(V_{f1}\) signal on the \(k_y\)-f diagrams for (a) \((x,z)=(18~{\rm{cm}}, 30~{\rm{cm}})\) and (b) \((-18~{\rm{cm}}, 30~{\rm{cm}})\), together with the dispersion curve of the magnetosonic wave propagating perpendicular to the magnetic field, where the dashed lines show \(k_y=0\). The fluctuation propagates in the azimuthal direction and is identified as the magnetosonic wave. (c) x profile of \(\Re [S_{nv}(f)]\), being equivalent to the wave-driven and frequency-decomposed cross-field electron flux. The cross-field inward electron flux is driven by the magnetosonic wave around 40 kHz. (d) x profile of the cross-phase between \(\tilde{n}_p(t)\) and \(\tilde{v}_e(t)\) for the frequency range of \(42\pm 1\) kHz, together with the yellow-colored region corresponding to the flux directed to the positive x direction. The phase data identifies the inward electron flux toward the main axis as well as \(\Re [S_{nv}(f)]\) in (c). (e) The calculated ratio of \(\alpha = |E_{\perp }/E_{\parallel }|\) for the dispersion branch in (a, b), where \(E_{\parallel }\) and \(E_{\perp }\) are the electric fields parallel and perpendicular to the wavenumber, respectively. The calculated \(\alpha\) close to zero in the frequency range higher than \(f_{ci}\) and lower than \(f_{LH}\) implies that the magnetosonic wave branch behaves like an electrostatic mode.