Electron ‐ whistler interaction at the Earth's bow shock: 1. Whistler instability

Abstract

The interaction of whistler waves with the electrons in the Earth's quasi‐perpendicular bow shock of November 7, 1977, is considered. A Monte Carlo simulation which includes the effect of electrostatic noise is used to obtain the electron distribution function fnof;e across the shock layer. The simulated fnof;e is rather anisotropic and in the shock foot has a marked loss cone structure which is evident in the data, too; therefore we study the instability of fnof;fe with respect to the emission of whistler modes. Strong whistler emission from the electrons is found, with frequency and spatial dependencies of the growth rate in good agreement with the observed magnetic noise. Most of the whistlers are generated in the shock foot, where the loss cone in the electron distribution function is found. This indicates that in quasi‐perpendicular collisionless shock, besides the reflected ion beam and the field‐aligned electron beam, an important source of whistler mode waves is the electron loss cone due to reflection from the magnetic ramp.