ULF ELF MONOCHROMATIC OSCILLATIONS OBSERVED BY PROGNOZ-8 AND PROGNOZ-10 SPACECRAFTS DURING QUASI-PERPENDICULAR SUPERCRITICAL SHOCK CROSSINGS/

The present paper analyses electromagnetic turbulence in the frequency range 0.1-75 Hz, associated with the supercritical quasiperpendicular crossings of the Earth's bow shock recorded by the Prognoz-8 and -10 satellites. The quasimonochromatic waves are identified in the shock t ransition region. Their frequencies, lying in the range 2-5 Hz upstrea m from the shock ramp, shift to a value less than 1 Hz in the downstre am region. The amplitudes of these narrow remissions are great enough to provide the primary dissipation in the flow of the solar wind plasm a. Electromagnetic oscillations with such properties are likely to be generated during non-linear evolution of the shock front, rather than by the instabilities driven by ion and electron drifts. Emissions with frequencies higher than 5 Hz have much smaller amplitudes and may be driven by lower hybrid-like instabilities.