Recent observations of auroral kilometric radiation (AKR) reported by James [1980] from the ISiS 1 data shows that in the generation region the AKR is downcoming, propagating at an angle between 60 ø and 90 ø with respect to the magnetic field, and that the local plasma frequency is much less than the local electron gyrofrequency. James points out that the theories of Wu and Lee [1979] and Roux and Pellat [1979] are

A hybrid simulation model with kinetic ions, massless fluid electrons, and phenomenological resistivity is used to study the perpendicular configuration of the bow shocks of the earth and other planets. We investigate a wide range of parameters, including the upstream Mach number, electron and ion beta (ratios of thermal to magnetic pressure), and resistivity. Electron beta and resistivity are found to have little effect on the overall shock structure. Quasi-stationary structures are obtained at moderately high ion beta (/3i '• 1), whereas the shock becomes more dynamic in the low ion beta, large Mach number regime (/3i '• 0.1, MA > 8). The simulation results are shown to be in good agreement with a number of observational features of quasi-perpendicular bow shocks, including the morphology •'• of the reflected ion stream, the magnetic field profile throughout the shock, and the Mach number dependence of the magnetic field overshoot.

The highly localized acceleration of electrons at the foreshock reported by Anderson et al. (1979) is explained in terms of a fast Fermi process. The basic notion is that in the solar wind frame the nearly perpendicular bow shock at the point of tangency of the interplanetary magnetic field acts as a fast‐moving magnetic mirror which can reflect electrons with sufficiently large pitch angles. The reflection process can effectively energize electrons and drive them upstream. If the seed electrons have energies of several hundred electron volts, they can attain energies of several keV through the acceleration process.

Simulations of a high Mach number shock with parameters typical of the earth's bow shock have been performed using a hybrid (particle ions, fluid electrons) code. The simulations reproduce the observed ion reflection and overshoots in the magnetic field and density. These features are shown to be closely associated with ion gyration.

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