ELECTRON WHISTLER INTERACTION AT THE EARTHS BOW SHOCK .1. WHISTLER INSTABILITY

The interaction of whistler waves with the electrons in the Earth's qu asi-perpendicular bow shock of November 7, 1977, is considered. A Mont e Carlo simulation which includes the effect of electrostatic noise is used to obtain the electron distribution function f(e) across the sho ck layer. The simulated f(e) is rather anisotropic and in the shock fo ot has a marked loss cone structure which is evident in the data, too; therefore we study the instability of f(e) with respect to the emissi on of whistler modes. Strong whistler emission from the electrons is f ound, with frequency and spatial dependencies of the growth rate in go od agreement with the observed magnetic noise. Most of the whistlers a re generated in the shock foot, where the loss cone in the electron di stribution function is found. This indicates that in quasi-perpendicul ar collisionless shock, besides the reflected ion beam and the field-a ligned electron beam, an important source of whistler mode waves is th e electron loss cone due to reflection from the magnetic ramp.