Localized Neutral Temperature Responses to Magnetospheric Energy Inputs and Gravity Wave Effects in the Polar Region

This study aims to model the large neutral temperature enhancement and temperature inversion layer (TIL) around 130 km observed by the Fe Boltzmann lidar at McMurdo, Antarctica, on 28 May 2011 when a coronal mass ejection reached the earth. Since atmospheric waves alone are difficult to induce temperature perturbations of ±250 K within the altitude range of 120-150 km, the sharp temperature gradients associated with this thermospheric TIL (TTIL) imply that other localized magnetospheric energy deposition may have taken place. To investigate the TTIL formation mechanism, we use the TIEGCM constrained by observations. Comparisons with the COSMIC and GRACE data show that the electron density is reasonably reproduced by TIEGCM, but neutral density is underestimated by 20% sometimes in the default model run (2.5°×2.5°). The TTIL feature is also missing from the model. Since the TTIL is observed when active aurora approached McMurdo according to the DMSP-SSUSI measurements, we first incorporate user-defined aurora energy flux maps into the model to tune it towards observations. Secondly, we use AMIE convection patterns to replace the default high-latitude empirical convection model. Thirdly, we derive the vertical profiles of Pedersen and Hall conductivity from the GLOW model using the DMSP observations, from which we find the model notably underestimates local conductivity near the lidar site. Since GLOW is almost fully driven by particle/energy precipitation, the underestimation of conductivity in TIEGCM is likely caused by the underestimation of particle/energy precipitation. We increase conductivity locally in TIEGCM by a certain factor, but the model responses suggest that this is insufficient to account for the temperature enhancement and TTIL formation. It is therefore necessary to consider other localized effects as well as include gravity wave-induced perturbations. Our study demonstrates how the ground-truth observations, in combination with models, may help study the localized responses of geospace to geomagnetic activities.