Journal of Geophysical Research: Space Physics

Electron number density fluctuations near the plasmapause observed by the CRRES Spacecraft


  • M. J. LeDocq,

  • D. A. Gurnett,

  • R. R. Anderson


Large quasi-periodic fluctuations in the electron number density are often encountered near and inside the plasmapause by the CRRES satellite. A power spectral analysis reveals electron density fluctuations with frequencies ranging from 2 mHz to approximately 61 mHz. Plasma density irregularities in the outer plasmasphere sometimes have power spectral slopes near −5/3, which suggest the presence of well-developed two-dimensional magnetohydrodynamic turbulence. Quasi-periodic fluctuations have been found outside the plasmasphere with spatial scales along the orbit path of approximately 750 km. A statistical analysis shows that the density fluctuation amplitudes are largest between L = 3 and L = 6, the region in which the plasmapause is located. The density fluctuation amplitudes decrease with increasing L shell for L > 6. Normalized fluctuation amplitudes greater than 10% are found in only 25% of the available data of this study. A significant magnetic local time dependence cannot be found due to incomplete data availability during the 9.00 to 14.99 MLT and the 15.00 to 20.99 MLT sectors.