Analysis of E×B drifts in Earth’s magnetosphere during geomagnetic
reversals: potential consequences for plasmasphere behavior and
stability
Abstract
Geomagnetic pole reversals occur frequently throughout geologic history,
although one has not yet occurred in recorded time. Magnetohydrodynamic
models of Earth’s core have revealed that during a reversal, the
magnetic dipole moment disappears, leaving higher-order moments.
Previous research examined quadrupole magnetic field topologies and
quantitatively specified the magnetic equators of those topologies but
did not fully examine charged particle drift motion and stability in the
inner magnetosphere. Earth’s closed magnetosphere is primarily dominated
by two electric fields, the corotational and convection generated
electric fields. E x B drifts from these fields ultimately drives the
behavior of the cold plasma of the plasmasphere. In a
quadrupole-dominated magnetic field, the plasma motion generated by the
E x B drifts would be dramatically different from the classical dipole
field plasma convection. Three quadrupole topologies were evaluated, and
the E x B drift was analyzed along the magnetic equators of these
topologies to characterize and quantify the resultant plasma motion and
evaluate the behavior, structure and stability of the plasmasphere. We
also tested for plasmaspause and magnetopause boundary sensitivity to
magnetic field strength. The direction of the convection flow is
hemispherically dependent for the η = 0 and 0.5 quadrupole topologies,
that is, the plasma in the Northern Hemisphere convects tailward, and
the Southern Hemisphere convects sunward. The η = 1 topology
demonstrates evidence of strong plasmasphere erosion due to the
intersection of the magnetic equators, and is particularly sensitive to
reductions in magnetic field strength.