Premium
Non‐thermal plasma observations using EISCAT: Aspect angle dependence
Author(s) -
Winser K. J.,
Lockwood M.,
Jones G. O. L.
Publication year - 1987
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl014i009p00957
Subject(s) - plasma , incoherent scatter , physics , anisotropy , thermal , ion , spectral line , computational physics , range (aeronautics) , line of sight , ionosphere , atomic physics , materials science , optics , geophysics , astrophysics , meteorology , astronomy , quantum mechanics , composite material
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.