Impacts of Geomagnetic storms on the mid-latitude mesosphere and lower thermosphere observed by a Na lidar and TIMED/GUVI

In this paper, we report our findings on the correlation between the neutral temperature (around the mesopause) and thermospheric column density O/N2 ratio, along with their response to geomagnetic storms above mid-latitude of North America. A temperature/wind Doppler Na lidar, operating at Fort Collins, CO (41°N, 105°W) and later at Logan, UT (42°N and 112°W), observed significant temperature increases (temperature anomaly) above 95 km (as much as 55 K at 105 km altitude) during four geomagnetic storms (April 2002, Nov. 2004, May 2005 and Oct. 2012). Coincident TIMED/GUVI observations indicate significant depletion in the thermospheric O/N2 ratio at the lidar locations. These observations suggest that the local mesopause warming seen by the lidar is due to transport of the high-latitude Joule and particle heated neutrals at the E and F layers to the mid-latitude region.