Meteor luminous efficiencies from simultaneous multi-frequency radar and high-resolution optical observations

We examine the effects of assumptions in the calculation of electron line density of radar meteors on the value of luminous efficiency calculated using simultaneous radar and optical observations. We combine high-resolution optical measurements from the Canadian Automated Meteor Observatory (CAMO) with multi-frequency radar echoes from the Canadian Meteor Orbit Radar (CMOR). Previous work relating β and τ has been limited to single-frequency radar observations, which requires additional modelling assumptions such as the initial trail radius (Weryk and Brown, 2013). In this work, we require model fits to all three frequencies at which CMOR operates, which provides better constraints which reduce the need for these assumptions, at the cost of significantly shrinking the pool of suitable data. Between 2017–2022, 299 candidates for three-frequency CMOR simultaneously observed by CAMO were identified, of which 1% were suitable for fitting. Although the fittable data set was too small to determine statistical trends, all events showed lower luminous efficiencies than those that would be found through single-frequency modelling. This emphasizes the need for better models of scattering from meteor trails in these studies. • Three-frequency radar fits produce lower luminous efficiency than single-frequency. • Few simultaneous radar+optical meteors fit all frequencies, highlighting fragmentation. • Luminous efficiencies constrained to ̃0.1%–1% using simultaneous radar+optical data. • Initial trail radius from multi-frequency fits disagree with previous assumptions.