Plasma and Electromagnetic Simulations of Meteor Head Echo Radar Reflections |
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Authors: | Lars Dyrud Derek Wilson Steiner Boerve Jan Trulsen Hans Pecseli Sigrid Close Chen Chen Yoonjae Lee |
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Institution: | (1) Center for Remote Sensing Inc, Fairfax, VA, USA;(2) Norwegian Defense Research Establishment, Kjeller, Norway;(3) University of Oslo, Oslo, Norway;(4) Las Alamos National Laboratory, Las Alamos, New Mexico |
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Abstract: | Recently, meteor head echo detections from high powered large aperture radars (HPLA) have brought new measurements to bear
on the study of sporadic interplanetary meteors. These same observations have demonstrated an ability to observe smaller meteoroids
without some of the geometrical restrictions of specular radar techniques. Yet incorporating data from various radar reflection
types and from different radars into a single consistent model has proven challenging. We believe this arises due to poorly
understood radio scattering characteristics of the meteor plasma, especially in light of recent work showing that plasma turbulence
and instability greatly influences meteor trail properties at every stage of evolution. In order to overcome some of the unknown
relationships between meteoroid characteristics (such as mass and velocity) and the resulting head echo radar cross-sections
(RCS), we present our results on meteor plasma simulations of head echo plasmas using particle in cell (PIC) ions, which show
that electric fields strongly influence early stage meteor plasma evolution, by accelerating ions away from the meteoroid
body at speeds as large as several kilometers per second. We also present the results of finite difference time domain electromagnetic
simulations (FDTD), which can calculate the radar cross-section of the simulated meteor plasma electron distributions. These
simulations have shown that the radar cross-section depends in a complex manner on a number of parameters. In this paper we
demonstrate that for a given head echo plasma the RCS as a function of radar frequency peaks at sqrt (2*peak plasma frequency)
and then decays linearly on a dB scale with increasing radar frequency. We also demonstrate that for a fixed radar frequency,
the RCS increases linearly on a dB scale with increasing head echo plasma frequency. These simulations and resulting characterization
of the head echo radar cross-section will both help relate HPLA radar observations to meteoroid properties and aid in determining
a particular radar facility’s ability to observe various meteoroid populations. |
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Keywords: | Meteors Radar Meteor head echoes |
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