Abstract
Electron phase space holes (EHs) associated with electron trapping are commonly observed as bipolar electric field signatures in both space and laboratory plasma. Until recently, it has not been possible to resolve EHs in electron measurements. We report observations of EHs in the plasma sheet boundary layer, here identified as the separatrix region of magnetic reconnection in the magnetotail. The intense EHs are observed together with an electron beam moving toward the X line, showing signs of thermalization. Using the electron drift instrument onboard the satellites of the Magnetospheric Multiscale mission, we make direct millisecond measurements of the electron particle flux associated with individual electron phase space holes. The electron flux is measured at a millisecond cadence in a narrow parallel speed range within that of the trapped electrons. The flux modulations are of order unity and are direct evidence of the strong nonlinear wave–electron interaction that may effectively thermalize beams and contribute to transforming directed drift energy to thermal energy.
Highlights
Wave–particle interactions are one of the fundamental ways energy is transferred and redistributed in fully or partially collisionless plasmas
Due to the often small time and length scales involved, studying the physics of these wave–particle interactions is only possible in situ within the Heliosphere and requires that instrumentation dedicated to wave–particle interaction of varying strength and character be a part of future space-plasma missions
We have presented observational evidence of the continuous spatiotemporal modulation of electron particle flux associated with a series of Electron phase space holes (EHs)
Summary
Wave–particle interactions are one of the fundamental ways energy is transferred and redistributed in fully or partially collisionless plasmas. Due to the often small time and length scales involved, studying the physics of these wave–particle interactions is only possible in situ within the Heliosphere and requires that instrumentation dedicated to wave–particle interaction (see, e.g., Dombrowski et al and references therein30) of varying strength and character be a part of future space-plasma missions This manuscript is organized in the following manner: in Sec. II, we present an overview of the magnetotail event and detailed measurements of the ESW properties that identify them as EHs; in Sec. III, we use the measured wave properties to reconstruct a 1D model of electron phase space and compare it to the observed electron flux; and in Sec. IV, we discuss our results
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