Magnetic Perturbations in Electron Phase-Space Holes: Contribution of Electron Polarization Drift

Electron phase-space holes, sometimes referred to as electron holes, are Debye-scale plasma structures commonly observed in space plasmas. Although they are usually thought of as electrostatic structures, recent observations have shown that these structures are often accompanied by magnetic field perturbations. Such magnetic perturbations may originate from Lorentz transformation of the electric field, although it has been also suggested that localized currents caused by the electron E x B motion may also play a role. In this paper, we consider the contribution of electron polarization drift to the current and therefore the magnetic field perturbations, which is validated by comparison to Magnetospheric MultiScale observations of 69 electron holes based on a superposed epoch technique. Our results show that the magnetic perturbations caused by the electron polarization drift can be significant compared to Lorentz transformation effect, especially in regions with low magnetic strength and large electron density.