Abstract.Radars frequently detect meteor trails created by the ablation of micro-meteoroids between 70 and 120 km altitude in the atmosphere. Plasma simulations show that density gradients a.t the edges of meteor trails drive gradientdrift instabilities which develop into waves with perturbed electric fields often exceeding hundreds of mV/m. These waves create an anomalous cross-field diffusion that can exceed the cross-field (2_ B) ambipolar diffusion by an order of magnitude. The characteristics of the instabilities and anomalous diffusion depend on the trail altitude, latitude, and density gradient. A simple relation defines the minimum altitude at which meteor trail density gradients drive plasma instabilities and anomalous diffusion. These results impact a number of meteor radar studies, including those that use diffusion rates to determine trail altitude, and atmospheric temperature.

Abstract. Using analytical models and kinetic simulations, this paper shows that weakly ionized meteor trails near the geomagnetic equator evolve through three distinct stages. First, a large electric field is generated perpendicular to both the geomagnetic field and the trail. Second, plasma density waves grow asymmetrically across the trail. Third, turbulence develops in the trails. Throughout this process, the electron E x B-drift velocity plays an essential role in controlling the motion of the trail. These plasma dynamics have important implications for the interpretation of meteor radar echoes.

[1] Field-aligned plasma density irregularities detected as nonspecular echoes by radars with large aperture-power products indicate the presence of plasma turbulence within meteor trails. This paper presents two-dimensional simulations of meteor trail instabilities and compares these results with theory and observations. In particular, this paper describes techniques for simulating trail turbulence and then discusses two sample cases using realistic plasma density gradients, masses, and atmospheric conditions appropriate for a 102-km altitude. In the first case, the trail lies along the geomagnetic field, B. In the second, it lies perpendicular to B and is subject to a small external electric field pointing parallel to it. These cases show the spontaneous development of instabilities leading to turbulence and field-aligned irregularities. These irregularities can create nonspecular echoes with broad spectral lines and small Doppler shifts similar to those observed by radars with large aperture-power products. The simulations also show turbulenceenhanced cross-field diffusion rates. Finally, the paper describes simulations of trails containing multiple ion species and shows how turbulent mixing greatly reduces species fractionation.