How neutral is quasi-neutral: Charge Density in the Reconnection Diffusion Region Observed by MMS | CU Experts

Magnetic reconnection is responsible for the major reconfigurations of; the magnetosphere that lead to energy transport and deposition into the; ionosphere. The fast rate at which magnetic energy is converted to; plasma kinetic energy is likely enabled by the polarization Hall; electric field that results from the separation of ions and electrons at; small scales. Signatures of Hall fields have played a key role in; identifying and studying reconnection, but the density of accumulated; charge has not been quantified. We use the 4-point measurements of the; Magnetospheric Multiscale mission to compute the divergence of the; electric field and present the first observations of charge density in; the diffusion region of magnetic reconnection. We show how it ties into; the Hall system, discuss measurement uncertainties, analyze quality; estimates, and make comparisons to 2D simulations. Charge density is; briefly presented for other phenomena, and ranges from 2% or less of; the background plasma density for magnetic reconnection and; electron-scale magnetic holes and peaks to upwards of 4% for electron; phase space holes.

Argall M; Shuster J; Dors I; Genestreti K; Nakamura T; Torbert R; Webster J; Ahmadi N; Ergun R; Strangeway R

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