Ion Temperature Anisotropy Measured in Regions of Strong Electric Fields Adjacent to Auroral Arcs
Ion Temperature Anisotropy Measured in Regions of Strong Electric Fields Adjacent to Auroral Arcs
Previously Published Material: Some of these findings were recently accepted pending minor review in "ESA's Swarm Mission, One Year in Space", a special edition of GRL.
Abstract ID#: 35211
English Abstract:
The Swarm satellites observe strongly anisotropic ion temperatures at 500 km altitude with temperature anisotropy ratios varying from 2 to 10. Coincident measurements with THEMIS All-Sky imagers suggest that these highly localized regions of ion heating are associated with strong electric fields at the edge of auroral precipitation. The ion temperature enhancements appear to depend on electric field strength and are comparable to what is expected from ion frictional heating theory. However, the observed perpendicular-to-parallel temperature ratios exceed the values predicted by existing calculations of collisional heating by as much as a factor of 2 in the strongest flows. If these observations are an accurate representation of the steady state collisional environment, they suggest that the collisional cross-sections currently used in collisional heating calculations should be revised. However it is also possible that the measurements are not made in a steady state environment, in which case a velocity distribution dispersion associated with vertical transport and occurring on a scale of minutes would also be able to affect the observed anisotropies.
Back to: The Physics of the Aurora I