Multisatellite Observations of Ion Holes in the Earth's Plasma Sheet

• We present the first observations of electrostatic solitary waves with electrostatic potential of negative polarity around a fast plasma flow in the Earth's plasma sheet. The solitary waves are observed aboard four Magnetospheric Multiscale spacecraft, which allowed accurately estimating solitary wave properties. Based on a data set of 153 solitary waves, we show that they are locally one-dimensional Debye-scale structures with amplitudes up to 20% of local electron temperature and they propagate at plasma frame speeds ranging from a tenth to a few ion-acoustic speeds at arbitrary angles to the local magnetic field. The solitary waves are associated with multi-component proton distributions and their velocities are around those of a beam-like proton population. We argue that the solitary waves are ion holes, nonlinear structures produced by ion-streaming instabilities, and conclude that once ions are not magnetized, ion holes can propagate oblique to local magnetic field.

Ämnesord

NATURVETENSKAP  -- Fysik -- Fusion, plasma och rymdfysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Fusion, Plasma and Space Physics (hsv//eng)

Nyckelord

plasma sheet

solitary waves

ion holes

electrostatic instabilities

ion beam instabilities

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