Ion-Acoustic Waves in the Solar Wind.
Abstract
Plasma wave measurements on the Helios 1 and 2 spacecraft have revealed the occurrence of electric field turbulence in the solar wind at frequencies between the electron and ion plasma frequencies. Wavelength measurements with the IMP 6 spacecraft now provide strong evidence that these waves are short wavelength ion-acoustic waves which are doppler shifted upward in frequency by the motion of the solar wind. Comparison of the Helios results with measurements from the earth-orbiting IMP 6 and 8 spacecraft shows that the ion-acoustic wave turbulence detected in interplanetary space has characteristics essentially identical to bursts of electrostatic turbulence generated by protons streaming into the solar wind from the earth's bow shock. In a few cases enhanced ion-acoustic wave intensities have been observed in direct association with abrupt increases in the anistropy of the solar wind electron distribution. This relationship strongly suggests that the ion-acoustic waves detected by Helios far from the earth are produced by an electron heat flux instability, as suggested by Forslund. Possible related mechanisms which could explain the generation of ion-acoustic waves by protons streaming into the solar wind from the earth's bow shock are also considered. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1977
- Accession Number
- ADA039092
Entities
People
- Donald A. Gurnett
- Louis A. Frank
Organizations
- University of Iowa