SuperDARN Evidence for Convection‐Driven Lagrangian Coherent Structures in the Polar Ionosphere

Abstract

AbstractPolar cap patches are large sporadic enhancements of plasma density on the scale of hundreds of kilometers, which can impact the performance of Global Navigation Satellite Systems. Lagrangian Coherent Structures (LCSs) are ridges that show areas of maximal separation in a time‐evolving flow. Previous work based on modeled ionospheric flow showed that LCSs exist in the ionosphere and are barriers governing patch formation. In this work, we identify the first data‐driven LCSs in the high‐latitude ionosphere using Super Dual Auroral Radar Network (SuperDARN) ion convection fields. The LCSs found using the Ionosphere‐Thermosphere Algorithm for LCSs are compared during geomagnetically quiet and active periods. The shape of the LCS is found to be dependent on the electric potential pattern. A consistent two‐cell pattern results in a W‐shaped LCS, but when the two‐cell pattern breaks down, the LCS loses this characteristic shape. The changes in the electric potential, and thus the LCS, are likely due to changes in the interplanetary magnetic field. A comparison between LCSs obtained from empirical models and data reveal that the data‐driven LCSs are poleward of and have a shorter longitudinal span than the model‐based LCSs. A comparison of the LCS location and the formation of a polar cap patch on 17 March 2015 showed that the center of the patch developed from plasma on the main LCS ridge, and this is confirmed with a separate polar cap patch event from 26 September 2011.