High-latitude ionospheric conductivity variability in three dimensions

Monday, August 8, 2016

We perform the first ever global-scale, altitude-dependent analysis of polar ionospheric conductivity variability using spectrally-resolved in-situ satellite particle measurements.  Our results show that height-integrated conductance and height-dependent conductivities are distinctly different. This difference underscores the importance of studying the ionosphere in three dimensions. We provide the framework for future three-dimensional global analysis of ionosphere-magnetosphere coupling.

Average EOFs in the E-Region ionosphere image
The mean and first three modes of variability (average EOFs) in the E-Region ionosphere for: (a) Hall conductivities (σH) and (b) Pedersen conductivities (σP). Mean patterns are along the top of (a) and (b) with a linear color scale (yellow to red) and EOFs are beneath the mean patterns with a diverging color scheme (blue to red) and scaled to a -0.5 to 0.5 range. The altitude increases from left to right . Each polar plot is oriented with the sun off to the top of the figure, dawn to the right, and dusk to the left and displays the distributions in AACGM coordinates. The percentage of the over all variability captured by each EOF is given in blue at bottom right.

With an empirical orthogonal function (EOF) analysis we identify three primary modes of three-dimensional variability related to ionospheric footprints of the quiet and disturbed geospace environment: 1) perturbation of the quasi-permanent auroral oval; 2) differing projections of electron precipitation during southward and northward interplanetary magnetic field; and 3) a likely imprint of variation in Alfvénic Poynting flux deposition. Together these modes account for >50% of the total conductivity variability throughout the E-Region ionosphere.

This manuscript was submitted to Gephysical Research Letters.