Monitoring of lower thermospheric neutral density variations using meteor head echoes

Abstract

Observations of neutral density in the mesosphere and lower thermosphere (MLT) region of the terrestrial atmosphere are important for understanding lower atmospheric, geomagnetic, and anthropogenic forcing. This study introduces a statistical method for measuring neutral density variations using an extensive dataset of meteor head echoes that were observed using the MAARSY high-power large-aperture (HPLA) mesosphere–stratosphere–troposphere (MST) radar. The method relies on observing the mean geocentric velocity of meteor head echoes as a function of initial detection altitude and day-of-year. The meteor head echo catalog used contains 1.4 million meteor head echoes between 2016–2023. Neutral density variations are observed with a 6 d time and 2 km altitude resolution between 85–115 km. The measurements show variations in neutral density potentially due to geomagnetic and atmospheric events. Variations of up to 20 % are common in the dataset, and agree with the magnitude of atmospheric neutral density fluctuations from an Upper-Atmosphere ICOsahedral Non-hydrostatic (UA-ICON) atmosphere model run.