SA13B-2351
Characterization of Non-Specular Meteor Trail Radar Detections from Non-Field-Aligned Irregularities
Characterization of Non-Specular Meteor Trail Radar Detections from Non-Field-Aligned Irregularities
Monday, 14 December 2015
Poster Hall (Moscone South)
Abstract:
Meteoroids enter the Earth’s atmosphere and are detected by radars as they ablate between 140 and 70 km altitude in the E-region of the ionosphere. The radar returns are classified as head echoes, the plasma surrounding the meteoroids, and trails, the expanding plasma column left in the meteoroid’s wake. In addition, plasma trails are categorized by the angle between the meteoroid’s trajectory and the radar beam. One type is the specular trail, which occurs when the meteoroid travels quasi-perpendicular to the beam. The second type, non-specular trail, is independent of trajectory but, according to our current understanding, the radar beam must be perpendicular to the Earth’s magnetic field in order to reflect from field-aligned irregularities (FAI) after the onset of plasma turbulence.However, the Southern Argentina Agile Meteor Radar (SAAMER) has surprisingly detected 25 cases of non-specular trails over a period of 12 days in 2011. At the radar’s location, the geomagnetic field is about 51 degrees with respect to the radar beam, which suggests that our present theory of the physics behind non-specular trail formation is lacking. We present interferometric results from the observations performed using SAAMER in order to demonstrate that the non-specular trails detected are due to reflections from non-FAI. We examine the detected trail duration dependence on altitude, meteoroid velocity, time of day, and various geometric relationships to establish that the plasma turbulence mainly arises from gradient drift and wind driven instabilities. Moreover, the latter parameters are compared to traditional non-specular trail observations from an equatorial high-power large aperture radar, ARPA Long-Range Tracking and Instrumentation Radar (ALTAIR), to contextualize the detections accomplished by SAAMER.