First 3‐D simulations of meteor plasma dynamics and turbulence

Abstract

Millions of small but detectable meteors hit the Earth's atmosphere every second, creating trails of hot plasma that turbulently diffuse into the background atmosphere. For over 60 years, radars have detected meteor plasmas and used these signals to infer characteristics of the meteoroid population and upper atmosphere, but, despite the importance of meteor radar measurements, the complex processes by which these plasmas evolve have never been thoroughly explained or modeled. In this paper, we present the first fully 3‐D simulations of meteor evolution, showing meteor plasmas developing instabilities, becoming turbulent, and inhomogeneously diffusing into the background ionosphere. These instabilities explain the characteristics and strength of many radar observations, in particular the high‐resolution nonspecular echoes made by large radars. The simulations reveal how meteors create strong electric fields that dig out deep plasma channels along the Earth's magnetic fields. They also allow researchers to explore the impacts of the intense winds and wind shears, commonly found at these altitudes, on meteor plasma evolution. This study will allow the development of more sophisticated models of meteor radar signals, enabling the extraction of detailed information about the properties of meteoroid particles and the atmosphere.

Physics of meteor generated shock waves in the Earth’s atmosphere – A review

“…The degree of ionization in the meteor train depends on the so called ionization coefficient (McKinley, 1961;Jones, 1997;Jones et al, 2001;Weryk et al, 2013). The ionized meteor train, as an artifact of meteor passage through the atmosphere, can be either observed visually or detected by radar (Hocking et al, 2001;2016b), as the quasineutral plasma expands into the ambient atmosphere under height dependent ambipolar diffusion (Francey, 1963;Holway, 1965;Galligan et al, 2004;Oppenheim et al, 2015). Some aspects of the short lasting hyperthermal chemistry which take place on the boundaries of high temperature cylindrical meteor trains in the initial stages of postadiabatic expansion have been studied by Silber et al (2017a).…”

Modeling the Altitude Distribution of Meteor Head Echoes Observed with HPLA Radars: Implications for the Radar Detectability of Meteoroid Populations

“…This plasma region or head plasma is significantly smaller than the more common meteor trail, and thus usually requires high power and greater system sensitivity, via a large antenna aperture, in order to be detected as a head echo (e.g., Janches et al 2014a). Over the years, several theoretical and experimental studies have been actively conducted on head echoes, and those studies provided extensive information about the electromagnetic interactions in the meteor plasma (Close et al 2002(Close et al , 2004Chau & Woodman 2004;Mathews 2004;Janches et al 2008;Kero et al 2012;Marshall & Close 2015;Oppenheim & Dimant 2015;Dimant & Oppenheim 2017a, 2017b, and several others). Nevertheless, uncertainties still exist, especially with respect to the nature of the scattering mechanism responsible for the head echoes.…”

Linear feature detection algorithm for astronomical surveys – II. Defocusing effects on meteor tracks

“…Such an ion trail model would need an initial non-Gaussian density profile (Jones 1995) that expands anisotropically as it depends on the geomagnetic field direction (Oppenheim and Dimant 2015). A detailed modeling of this process is out of scope of our paper, hence, we use just an illustrative case with a Gaussian intensity profile and the initial width of 0.8 m (typically it is between ∼0.5 m and 3 m, depending on the altitude; Stokan et al 2013).…”

“…Hence, interaction of the meteor plasma with the surrounding atmosphere and ionosphere helps in investigations of the physical and chemical properties of the Earth atmosphere and its elec-trodynamics (e.g. Dyrud et al 2011;Plane 2012;Pellinen-Wannberg et al 2014;Oppenheim and Dimant 2015).…”