DEPENDENCE OF THE OCCURRENCE OF CHORUS UPON THE LOCATION OF THE PLASMAPAUSE.
Abstract
VLF emissions at 1.3 kHz are observed at altitudes below 1500 km by a VLF receiver aboard spacecraft OV3-3. Correlations of these emissions with local time, magnetic latitude, and the planetary magnetic index Kp show that they have the same characteristic dependence with these parameters as have chorus emissions observed by other satellites and by ground-based stations. The altitude dependence of the magnetic field intensity agrees with that predicted for a wave propagating completely trapped on a tube of force without attenuation. The occurrence of the emission increases with Kp and depends upon the location of the plasmapause. As the plasmapause moves to lower L-shells, the emission occurs more often. A possible explanation for this dependence is the relationship between the growth rate of the doppler-shifted cyclotron instability and the sharp decrease in electron density at the plasmapause. For frequencies near 1 kHz and electron energies in the range 0.05-1 MeV, the growth rate and region of maximum growth increase as the plasmapause moves to lower L-shells, in agreement with the experimental data. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 30, 1970
- Accession Number
- AD0704817
Entities
People
- Donald A. Mcpherson
- Harry C. Koons
Organizations
- The Aerospace Corporation