TY - JOUR
T1 - Radio science issues surrounding HF/VHF/UHF radar meteor studies
AU - Mathews, J. D.
N1 - Funding Information:
This effort was supported under NSF Grants ATM-0108600 and AST-0205848 to The Pennsylvania State University. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center which is operated by Cornell University under cooperative agreement with the National Science Foundation. As always we thank the Arecibo staff for their efforts.
PY - 2004/2
Y1 - 2004/2
N2 - Classical meteor radars depend on coherent (Fresnel) scattering from a meteor trail oriented perpendicular to the radar wave vector at closest approach to the radar. Meteor trails viewed in this manner are described as "classical" radar meteors with under/over-dense trails. While meteor "head-echoes" are rarely seen with classical low-power, wide-beam HF meteor radars, they are essentially always seen by large aperture (narrow-beam), high-power VHF/UHF radars. We discuss the expected radar scattering cross-sections (RCSs) of head-versus trail-echoes and how equilibrium concepts such as plasma frequency are of limited use in describing the results. Particular attention is given to the frequency dependence of the RCS and how the frequency dependence may yield considerable new information regarding the plasma distribution in the "coma" surrounding the meteoroid. As the head-echo is directly associated with the meteoroid, instantaneous (single-pulse) Doppler observations are possible. In the case of classical trail-echoes, the time evolution of the RCS as a function of frequency may provide new information on the plasma diffusion rate and thus on atmospheric density and temperature. Information from the time evolution of the trail must however be considered in light of new results showing that the trail rapidly B-field-aligns in a manner apparently driven by plasma instabilities that develop in 10-100 ms after trail deposition. It is in the context of instability-driven B-field alignment of the trails that we discuss anomalous trail-echoes. The anomalous trail-echo is a range-spread chaotic (non-classical) trail-echo derived from a meteor that travels at an arbitrary angle relative to the radar wave vector. We present theoretical simulations illustrating these concepts.
AB - Classical meteor radars depend on coherent (Fresnel) scattering from a meteor trail oriented perpendicular to the radar wave vector at closest approach to the radar. Meteor trails viewed in this manner are described as "classical" radar meteors with under/over-dense trails. While meteor "head-echoes" are rarely seen with classical low-power, wide-beam HF meteor radars, they are essentially always seen by large aperture (narrow-beam), high-power VHF/UHF radars. We discuss the expected radar scattering cross-sections (RCSs) of head-versus trail-echoes and how equilibrium concepts such as plasma frequency are of limited use in describing the results. Particular attention is given to the frequency dependence of the RCS and how the frequency dependence may yield considerable new information regarding the plasma distribution in the "coma" surrounding the meteoroid. As the head-echo is directly associated with the meteoroid, instantaneous (single-pulse) Doppler observations are possible. In the case of classical trail-echoes, the time evolution of the RCS as a function of frequency may provide new information on the plasma diffusion rate and thus on atmospheric density and temperature. Information from the time evolution of the trail must however be considered in light of new results showing that the trail rapidly B-field-aligns in a manner apparently driven by plasma instabilities that develop in 10-100 ms after trail deposition. It is in the context of instability-driven B-field alignment of the trails that we discuss anomalous trail-echoes. The anomalous trail-echo is a range-spread chaotic (non-classical) trail-echo derived from a meteor that travels at an arbitrary angle relative to the radar wave vector. We present theoretical simulations illustrating these concepts.
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U2 - 10.1016/j.jastp.2003.11.001
DO - 10.1016/j.jastp.2003.11.001
M3 - Article
AN - SCOPUS:1542350792
SN - 1364-6826
VL - 66
SP - 285
EP - 299
JO - Journal of Atmospheric and Solar-Terrestrial Physics
JF - Journal of Atmospheric and Solar-Terrestrial Physics
IS - 3-4
ER -