Charged particle scattering in dipolarized magnetotail

TL;DR

This paper reveals that localized magnetic field humps in the Earth's magnetotail can enhance energetic particle scattering and precipitation, challenging previous assumptions about the effects of curvature radius maxima.

Contribution

It demonstrates that off-equatorial minima in curvature radius caused by magnetic field humps can increase particle scattering, providing new insights into magnetotail current sheet diagnostics.

Findings

Localized magnetic humps create off-equatorial curvature minima.

Off-equatorial regions can enhance particle scattering and precipitation.

Results inform remote sensing of magnetotail structure.

Abstract

The Earth's magnetotail is characterized by stretched magnetic field lines. Energetic particles are effectively scattered due to the field-line curvature, which then leads to isotropization of energetic particle distributions and particle precipitation to the Earth's atmosphere. Measurements of these precipitation at low-altitude spacecraft are thus often used to remotely probe the magnetotail current sheet configuration. This configuration may include spatially localized maxima of the curvature radius at equator (due to localized humps of the equatorial magnetic field magnitude) that reduce the energetic particle scattering and precipitation. Therefore, the measured precipitation patterns are related to the spatial distribution of the equatorial curvature radius that is determined by the magnetotail current sheet configuration. In this study, we show that, contrary to previous thoughts, the magnetic field line configuration with the localized curvature radius maximum can actually enhance the scattering and subsequent precipitation. The spatially localized magnetic field dipolarization (magnetic field humps) can significantly curve magnetic field lines far from the equator and create off-equatorial minima in the curvature radius. Scattering of energetic particles in these off-equatorial regions alters the scattering (and precipitation) patterns, which has not been studied yet. We discuss our results in the context of remote-sensing the magnetotail current sheet configuration with low-altitude spacecraft measurements.