Plasma wave turbulence associated with an interplanetary shock

Abstract

In this paper we give a brief summary of the interplanetary shocks detected and analyzed to date from the Helios 1 and 2 spacecraft and present a detailed analysis of the plasma wave turbulence associated with one particular shock, on March 30, 1976. This event was selected because a very clearly defined burst of plasma wave turbulence occurs at the shock with otherwise quiet conditions in the solar wind upstream and downstream of the shock. The shock is an oblique shock and the upstream parameters are characterized by a low Mach number, a low beta, and an unusually large electron to ion temperature ratio. Three types of plasma waves are detected in association with this shock: (1) electron plasma oscillations, (2) electrostatic ion‐acoustic or Buneman mode turbulence from about 1 to 30 kHz, and (3) whistler‐mode magnetic noise. Because of the high velocity of the shock and the quiet conditions in the solar wind this event provides a particularly good determination of the scale size and characteristics of the precursor waves upstream of the shock and the electric and magnetic field turbulence in the wake behind the shock. The primary burst of electric and magnetic field noise at the shock occurs a few seconds after the jump in the magnetic field, with a broad maximum in the electric field intensities at about 3 kHz and a monotonically decreasing magnetic field spectrum below about 1 kHz. Many of the characteristics of this shock are found to be closely similar to, and are compared with, previous observations of plasma wave turbulence associated with the earth's bow shock.