Figure 1

Observations of drift vortices on a density gradient and coupled to an Alfvén wave, by the Cluster multispacecraft in the cusp region of the magnetosphere. See main text for a description of the coordinate system used. (a) shows four-spacecraft data, while (b)–(h) show data from $C2$. (a) Electron density showing the gradient. (b) Electric field perpendicular to the ambient magnetic field and along the density gradient. (c) Electric field perpendicular to the density gradient. (d) Perpendicular magnetic field along the density gradient. (e) Perpendicular magnetic field transverse to the gradient. (f) Parallel magnetic field. (g) Perpendicular current density. (h) Parallel current density. Note the different units for the current panels.Reuse & Permissions

Figure 2

Spacecraft trajectories and electric field from $C2$ (lower) and $C4$ (upper) in the $(\nabla n_e,{\mathbf{B}}_0\times \nabla n_e)$ plane. The center of the coordinate system is the instantaneous position of $C2$ at the time of maximum absolute amplitude of $E_{\nabla n}$. The yellow circle indicates the vortex size, with an inferred vortex radius of $r_0\approx 24\mathrm{km}=3{\rho }_s$.Reuse & Permissions

Figure 3

Estimate of the electrostatic potential $\varphi$ for vortex 1 integrated from the electric field perpendicular to the ambient magnetic field and along the spacecraft trajectory.Reuse & Permissions