Non-thermal plasma observations using EISCAT: Aspect angle dependence

Article English OPEN
Winser, K. J. ; Lockwood, Mike ; Jones, G. O. L. (1987)
  • Publisher: American Geophysical Union
  • Related identifiers: doi: 10.1029/GL014i009p00957
  • Subject:
    arxiv: Physics::Plasma Physics | Physics::Space Physics

Recent observations with the EISCAT incoherent scatter radar have shown large rises in dayside, auroral plasma velocities (>2 km s^{−1}) over a wide range of latitudes and lasting about an hour. These are larger than the neutral thermal speed, and allow, for the first time, observations of a non-thermal plasma over a range of observing angles, revealing a clear angular dependence. The observed ion temperature anisotropy, deduced by assuming a Maxwellian line-of-sight ion velocity distribution, is at least 1.75, which exceeds the theoretical value for a bi-Maxwellian based on a realistic ion-neutral collision model. The aspect angle dependence of the signal spectra also indicates non-Maxwellian plasma.
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