Kinetic Scale Magnetosheath Turbulence at Low Electron Beta

Plasma turbulence has been extensively studied at kinetic scales in the free solar wind at 1 AU where both ion and electron betas are typically order unity. However, this is not the case for other environments, e.g. close to the Sun both betas are much less than one, and in the Earth's magnetosheath the electron beta is often much less than one. Here, we present results from spacecraft observations in the Earth's magnetosheath. We show that a new type of turbulence develops at the electron inertial scale, which we term inertial kinetic Alfven turbulence. This turbulence is characterized by an increased magnetic compressibility, following a mode we term the inertial kinetic Alfvén wave, and a steeper spectrum of magnetic fluctuations, consistent with a spectral index of -11/3 that we obtain from a new set of nonlinear equations.