Geotail data across the distant magnetopause boundary, 82 Earth radii downtail. The top two panels show the velocity and density jump (solid lines) demarking the boundary crossing, while the third panel shows the ion pressure and magnetic pressure (solid and dotted lines, respectively), revealing that the ion pressure dominates both inside and outside of the boundary. The final panel shows the ion measurements as a function of particle energy, showing the change from magnetosheath plasma to magnetospheric properties. Credit: Artemyev et al., 2017, Figure 3a
Source: Journal of Geophysical Research: Space Physics

Space physicists like to focus on regional boundaries that are magnetized. Artemyev et al. [2017] examine a boundary where magnetic fields play only a marginal role: the far-downtail magnetopause. At distances from 50 to 200 RE downtail, they find that the pressure balance is dominated by the plasma on each side of the boundary, not the magnetic field change across the boundary. This is completely different from the dayside magnetopause, which is dominated by a magnetic field discontinuity. They find that the total energies of the ion populations inside and outside the boundary are similar, suggesting thermalization is sufficient to convert streaming magnetosheath ions into hot, rarified magnetotail ions inside the boundary.

Citation: Artemyev A.V, V. Angelopoulos, A. Runov, C.-P. Wang, and L.M. Zelenyi [2017], Properties of the equatorial magnetotail flanks 50-200RE downtail, Journal of Geophysical Research: Space Physics, 122,

 —Mike Liemohn, Editor-in-Chief, JGR: Space Physics

Text © 2018. The authors. CC BY-NC-ND 3.0
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