The emissions of broadband electrostatic noise in the near vicinity of the shuttle orbiter

Abstract

Measurements of the Space Shuttle environment from the STS-3 and Spacelab 2 missions indicate the presence of oblique ion streams and broadband electrostatic noise. A two-dimensional theoretical model is applied to study a possible causal relationship between the ion streams and the broadband noise; especially in terms of the ion acoustic wave and ion-ion wave modes. This model predicts the generation of waves with frequencies ranging from the ion cyclotron frequency up to values greater than the ion plasma frequency, with the maximum growth rate occurring in the 10 kHz range. These results are consistent with the observational data from the STS-3 mission. The model also shows that these two wave modes can co-exist only when the wave vectors of the two wave modes are nearly perpendicular. The parametric dependence of the wave instabilities on the plasma parameters, e.g. N b/ N e, T e/ T i and the inclination of the wave propagation vector, is also studied.