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Extreme plasma convection and frictional heating of the ionosphere: ISR observations
Author(s) -
Akbari H.,
Goodwin L. V.,
Swoboda J.,
St.Maurice J.P.,
Semeter J. L.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja023916
Subject(s) - incoherent scatter , ionosphere , physics , ion , computational physics , plasma , anisotropy , polarization (electrochemistry) , radar , scattering , atomic physics , f region , spectral line , geophysics , optics , nuclear physics , chemistry , telecommunications , quantum mechanics , astronomy , computer science
Extremely elevated ion temperatures observed with the Poker Flat and Resolute Bay incoherent scatter radars in the E and F regions of the polar ionosphere are discussed. Our observations include one‐dimensional, line‐of‐sight ion temperatures ( T i ,1 d ) that at times can rise to up to ∼8000°K. While examining the accuracy of the derived temperatures is difficult due to the several potential sources of error and uncertainty, we find that at altitudes of ∼130–250 km the line‐of‐sight ion temperatures obtained at relatively small aspect angles (for instance, at 22.5° away from the magnetic field direction) are below the expected values for the average or three‐dimensional ion temperatures ( T i ). We find that this difference matches well with the theoretical expectation from anisotropic ion velocity distributions that emerge from polarization elastic scattering collisions between NO + and N 2 . These results are therefore the clearest detection of anisotropic ion velocity distributions with the Poker Flat Incoherent Scatter Radar and Resolute Bay Incoherent Scatter Radar facilities. Moreover, at higher altitudes (>∼300 km), where the resonant charge exchange collisions prevail, and for a very high ion temperature event ( T i ∼8000°K), we observe that the incoherent scatter radar (ISR) spectra obtained at large aspect angles (e.g., 55°) look like those expected from non‐Maxwellian plasma. At similar altitudes, the measured one‐dimensional temperatures at an aspect angle of 22.5° are found to exceed the expected values from the frictional heating and resonant charge exchange collisions by about 1000°K. A portion of this offset is thought to reflect the role of Coulomb collisions.