Turbulence in fluids¹ and plasmas^{2, 3, 4, 5} is a ubiquitous phenomenon driven by a variety of sources—currents, sheared flows, gradients in density and temperature, and so on. Turbulence involves fluctuations of physical properties on many different scales, which interact nonlinearly to produce self-organized structures in the form of vortices^{2, 3, 4, 5}. Vortex motion in fluids and magnetized plasmas is typically governed by nonlinear equations^{2, 3, 4, 5}, examples of which include the Navier–Stokes equation^{1, 2}, the Charney–Hasegawa–Mima equations^{2, 3, 4, 5} and their numerous generalizations^{6, 7, 8, 9}. These nonlinear equations admit solutions^{2, 3, 4, 5} in the form of different types of vortices that are frequently observed in a variety of contexts: in atmospheres, in oceans and planetary systems^{2, 4}, in the heliosphere^{10, 11}, in the Earth's ionosphere and magnetosphere^{12, 13, 14, 15, 16, 17}, and in laboratory plasma experiments¹⁸. Here we report the discovery by the Cluster satellites¹⁹ of a distinct class of vortex motion—short-scale drift-kinetic Alfvén (DKA) vortices^{8, 9}—in the Earth's magnetospheric cusp region. As is the case for the larger Kelvin–Helmholtz vortices observed previously¹⁷, these dynamic structures should provide a channel for transporting plasma particles and energy through the magnetospheric boundary layers.

1. Laboratoire de Physique et Chimie de l'Environnement, CNRS, 45071 Orléans, France
2. Swedish Institute of Space Physics, SE-751 21 Uppsala, Sweden
3. Institut für Theoretische Physik IV, Ruhr-Universität Bochum, D-44780 Bochum, Germany
4. Centre d'Etude Spatiale des Rayonnements, Toulouse 31029, France

Correspondence to: David Sundkvist^1,2 Correspondence and requests for materials should be addressed to D.S. (Email: davids@irfu.se).

Received 15 March 2005; Accepted 16 June 2005

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