On the influence of background dust on radar scattering from meteor trails

Abstract

We consider the influence of a possible background of mostly non-visual neutral or positively charged dust, on the diffusion of the ionized meteor trails formed as meteors burn up in the atmosphere. The aim of this is to see if the decay time of such trails, which is used to determine the neutral gas temperature at the trail height, can be affected by a part of the trail electrons being absorbed by dust as they diffuse outward. In our model calculations we consider three different scenarios for the background dust ranging from small but numerous positively charged dust, which is reported being observed by rocket probes, to the larger but well-established population of often visible icy dust particles. We consider the icy dust particles during quiet night conditions when they for the most part will be electrically neutral. We find that the decay of mainly the weaker trails will be affected. For the stronger trails with their larger electron content the limited electron absorption capability of the background dust have a negligible effect on the radar echo decay time. We suggest that systematic investigations at different heights, time of day and year, to look for clear differences in decay times as a function of initial trail echo strength, can give information on a content of the elusive background of dust particles. In such an investigation, the presence of substantial amounts of small positive or neutral dust particles should lead to a significantly smaller apparent decay time for weak trails than for strong trails.