Observation of wake-induced plasma waves around an ionospheric sounding rocket

Abstract

Plasma waves generated around the plasma wake of a supersonically moving rocket are studied using data from an impedance probe and a wave receiver installed on the sounding rocket S-520-26. These instruments were used to measure the electron number density and plasma waves at 260 ms intervals, which allows four to five measurements per rotation. During the flight of the S-520-26, three types of plasma waves were observed: short-wavelength electrostatic waves such as electrostatic electron cyclotron harmonic waves, upper hybrid resonance mode waves, and whistler mode waves, assuming that the observed waves are produced in the near wake of the rocket. The wave generation mechanisms are discussed by calculating the linear growth rates of electrostatic waves; positive growth rates are obtained with the assumption of an anisotropic electron distribution function having a beam component or temperature anisotropy. We revealed the spatial distribution of the wave activity around the rocket and its relationship with the wake structure by analysis of the spin-phase dependence of the waves and the observed electron number density. The spin-phase dependence suggests that there are localized hot plasmas around the wake structure that can induce various types of plasma instability.