Neutral Air Density Variations Derived from Specular Meteor Echo Observation Spanning One Solar Cycle

Abstract:

Specular meteor radars (SMR) are a wide spread and established method to investigate mesospheric/ lower thermospheric (MLT) dynamics. Since 2002 the Canadian Meteor Orbit Radar (CMOR) conducts observations of meteor echoes in a fixed, stable configuration. Here we present measurements of the meteor peak flux altitude (MPFA) spanning one solar cycle at an altitude of 91 km. The MPFA is converted into neutral air density variations using a single body meteor ablation model and a NRLMSIS background atmosphere. We were able to separate the long term trend from the solar cycle effect assuming a linear trend and a sinusoidal solar cycle effect. The neutral air density shows a solar cycle signature of 2.4 +/-0.7% for solar cycle 23/24. The long term trend indicates a decreasing neutral air density of 5.8+/-1.1% per decade, which is in reasonable agreement to the model results of Akmaev et al., 2006. They predicted a decrease of neutral air density for the MLT in the order of 5-6% per decade due to greenhouse gas cooling.