Magnetohydrodynamic Waves Detected by Ice at Distances Equal-To 280,000,000-KILOMETERS from Comet p/ Halley - Cometary or Solar Wind Origin
Spectral analyses of the high resolution magnetic field data are employed to determine if there is evidence of cometary heavy ion pickup when ICE was closest to Halley, ∼ 28 106 km. No evidence is found for the presence of heavy ion cyclotron waves. However, from this search, two new wave modes are discovered in the solar wind: electromagnetic waves near the proton cyclotron frequency and drift mirror mode "waves". Both modes have scales of 10-60s (1 to 6 times the proton gyro period) in the spacecraft frame. The possibility of wave generation by cometary hydrogen pickup is explored. Theoretical arguments and further experimental evidence indicates that cometary origin is improbable. The most likely source is instabilities in high speed solar wind streams, presumably associated with stream-stream interactions. VLF electrostatic emissions are found to occur in field minima or at gradients of the drift mirror structures. Possible generation mechanisms of drift mirror mode waves, cyclotron waves and electrostatic waves are discussed.
Astronomy and Astrophysics
- Pub Date:
- November 1987