Triple-frequency meteor radar full wave scattering

G Stober,M Campbell-Brown,P Brown,R J Weryk

doi:10.1051/0004-6361/202141470

Abstract

Context. Radar scattering from meteor trails depends on several poorly constrained quantities, such as electron line density, q, initial trail radius, r0, and ambipolar diffusion coefficient, D. Aims. The goal is to apply a numerical model of full wave backscatter to triple frequency echo measurements to validate theory and constrain estimates of electron radial distribution, initial trail radius, and the ambipolar diffusion coefficient. Methods. A selection of 50 transversely polarized and 50 parallel polarized echoes with complete trajectory information were identified from simultaneous tri-frequency echoes recorded by the Canadian Meteor Orbit Radar. The amplitude-time profile of each echo was fit to our model using three different choices for the radial electron distribution assuming a Gaussian, parabolic-exponential, and 1-by-r2 electron line density model. The observations were manually fit by varying, q, r0, and D per model until all three synthetic echo-amplitude profiles at each frequency matched observation. Results. The Gaussian radial electron distribution was the most successful at fitting echo power profiles, followed by the 1∕r2. We were unable to fit any echoes using a profile where electron density varied from the trail axis as an exponential-parabolic distribution. While fewer than 5% of all examined echoes had self-consistent fits, the estimates of r0 and D as a function of height obtained were broadly similar to earlier studies, though with considerable scatter. Most meteor echoes are found to not be described well by the idealized full wave scattering model.

Highlights

Transverse radio wave scattering from meteor trails have been used to infer properties of the middle atmosphere and astronomical information related to the meteoroid environment of the Solar System for 70 yr (Baggaley 2009)
Meteor trail modeling efforts have focused on two distinct types of meteor echoes: meteor head echoes and Tables from full wave scattering model are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A108 non-specular echoes
We explored the recently proposed lateral Sugar model (LSM) or Dimant Oppenheim (DO) model (Dimant & Oppenheim 2017b; Sugar et al 2018) where the plasma distribution is approximated by the following equation: n(r, t)

Summary

Introduction

Transverse radio wave scattering from meteor trails ( called specular reflections) have been used to infer properties of the middle atmosphere and astronomical information related to the meteoroid environment of the Solar System for 70 yr (Baggaley 2009). The basic physics of electromagnetic scattering from a long cylindrical trail of electrons and ions has been understood in broad form since the late 1940s (Lovell & Clegg 1948; Herlofson 1951; Kaiser & Closs 1952; Poulter & Baggaley 1977; Ceplecha et al 1998) In addition to their original use in meteor astronomy for such questions as the meteoroid velocity distribution and meteoroid mass influx (Hocking 2000; Elford 2004; Holdsworth et al 2007; Stober et al 2011; Mazur et al 2020), transverse scatter radars have become standard observation systems for mesosphere and lower thermosphere dynamics. The other type of echo, nonspecular echoes (Dyrud et al 2007), are long-lived reflections driven either by plasma instabilities related to the orientation of the local geomagnetic field, rather than the orientation of the trail alone (Oppenheim et al 2003; Close et al 2008), or by the presence of charged dust (Chau et al 2014) operating on scales of seconds and hundreds of meters

Objectives

Results

Discussion

Conclusion