Direct Detection of Electron Demagnetization and Agyrotropy at Electron Diffusion Regions

The central focus of the non-ideal layers of collisionless reconnection is the electron diffusion region where field lines lose their traceability. This paper focuses on a new scalar observable, agyrotropy, for in situ and 3-D PIC certification of thermal electrons as being demagnetized, the essential property of the electron diffusion region. Hithertofore inferences of penetrations of the "electron diffusion region" have either centered on a magnetometer null reading in anti-parallel geometries, or a collection of tests involving only the electromagnetic field for guide geometries. These latter tests are not sufficient for the task of identifying the electron diffusion region. Examples of the incidence and onset of electron agyrotropy while traversing and near to current sheets will be presented from the Polar Hydra data at anti-parallel and guide field crossings of the magnetopause. Examples of the incidence and spatial distribution of electron agyrotropy expected from full PIC coded in open geometry will also be presented to motivate the labeling role that agyrotropy has for finding the electron diffusion regions, that is especially relevant in the guide geometry and 3d PIC simulations.