Extreme plasma convection and frictional heating of the ionosphere: ISR observations

Autor: Joshua Semeter, John Swoboda, J.-P. St.-Maurice, H. Akbari, L. V. Goodwin
Rok vydání: 2017
Předmět:
Zdroj: Journal of Geophysical Research: Space Physics. 122:7581-7598
ISSN: 2169-9402
2169-9380
DOI: 10.1002/2017ja023916
Popis: 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 (Ti,1d) 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 (Ti). 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 N2. These results are therefore the clearest detection of anisotropic ion velocity distributions with the PFISR and RISR facilities. Moreover, at higher altitudes (>∼ 300 km), where the resonant charge exchange collisions prevail, and for a very high ion temperature event (Ti∼ 8000 ° K), we observe that the 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.
Databáze: OpenAIRE
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