Plasma flow hypothesis in the magnetosphere relating to frequency shift of electrostatic plasma waves

Abstract

The frequency dynamic spectrum indicating a monotonic frequency shift of the electrostatic electron cyclotron harmonic wave emissions in the data of VLF electric field observations by Ogo 5 has been detected in the midnight and dawn meridians outside the plasmapause; the emissions are produced from turbulent areas in the plasma states that include the temperature anisotropy, loss cone velocity distribution, or the double hump in the velocity distribution function. The frequency shift is also observed for the case of the emissions in the magnetosheath near the subsolar point. These frequency shifts are interpreted on a hypothesis of the Doppler effects of the plasma waves due to the plasma flow with respect to the satellite frame. The speeds of the plasma flow are obtained and have a range from 150 to 300 km/s. Disruption of the plasma flow due to the magnetic field bumps may produce the turbulent source generating the Harris type or beam type instabilities that generate the electrostatic electron cyclotron harmonic waves.