Millisecond observations of nonlinear wave–electron interaction in electron phase space holes

Electron phase space holes (EHs) associated with electron trapping are commonly observed as bipolar electric field signatures in both and laboratory plasma. Until recently, it has not been possible to resolve EHs measurements. We report observations of the plasma sheet boundary layer, here identified separatrix region magnetic reconnection magnetotail. The intense together an beam moving toward X line, showing signs thermalization. Using drift instrument onboard satellites Magnetospheric Multiscale mission, we make direct millisecond measurements particle flux individual holes. is measured at a cadence narrow parallel speed range within that trapped electrons. modulations order unity evidence strong nonlinear wave–electron interaction may effectively thermalize beams contribute transforming directed energy thermal energy.