Interferometry observations of VHF backscatter from plasma irregularities induced by meteor in sporadic E region

Abstract

showed that the meter-scale plasma irregularities can be generated within the meteor trail through gradient drift/ Farley Buneman instability. Dyrud et al. [2001] further showed that these small scale irregularities will produce an anomalous cross-field diffusion of the meteor trail, leading to substantially reduction in the lifetime of the meteor trail echoes. [3] With spatial domain interferometry techniques, Chapin and Kudeki [1994b] and Reddi et al. [2002] found that the range spread echo regions are nearly parallel to the radar beam and the directions of the angle of arrival were not necessarily perpendicular to the geomagnetic field lines. Their results imply that the range spread meteor echoes are unlikely to come from the field-aligned irregularities due to appreciably large aspect angle. However, with beam swing technique, Zhou et al. [2001] found that numerous longlived range spread echoes were detected when the radar beam was pointed normal to magnetic field line, and the echoes were largely absent when the beam was pointed vertically and parallel to magnetic field line directions. They inferred that the plasma irregularities responsible for the range spread echoes are field-aligned, irrespective of no aspect sensitivity of the backscatter was measured. We will provide concrete evidence that, using interferometry methods to accurately position the targets in the echoing region, the meteor-induced range spread echoes may be highly aspect sensitive and the corresponding irregularities are field-aligned.