16 October 2007 Anisotropic refractive index fluctuations spectrum in the stratosphere sensed from balloon-borne observations of stellar scintillation
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Scintillation effects caused by the fluctuations of the refractive index of air are not negligible in the stratosphere. Recent experiments highlight the composite nature of optical turbulence in the stratosphere. We present an analytical model of scintillation based on a 3-D model of anisotropic and isotropic refractive index fluctuations spectrum that predicts scintillation rates inside the Rytov regime. This model uses a multi-layer decomposition of the turbulence profile. The effect of anisotropy leads to significant scintillation rates when a source is observed with a horizontal line of sight. Astronomical observations consisting in stellar scintillation made from balloon-borne spectrometer AMON-RA allow us to remotely probe statistical characteristics in the stratosphere, to validate the model of scintillation developed herein and to obtain refined values of its parameters. Data reduction from these observations brings out values of the inner scale of the anisotropic spectrum. We retrieve metric values of the inner scale that are compatible with space-based measurements. We find a major contribution of the anisotropic spectrum relatively to the isotropic contribution. This effect is particularly noticeable when the sight line plunges into the atmosphere, leading to strong scintillation as well as coupled chromatic refraction effects. This makes clear the presence of gravity waves in the stratosphere.
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Clélia Robert, Clélia Robert, Jean-Marc Conan, Jean-Marc Conan, Vincent Michau, Vincent Michau, Jean-Baptiste Renard, Jean-Baptiste Renard, Claude Robert, Claude Robert, Francis Dalaudier, Francis Dalaudier, } "Anisotropic refractive index fluctuations spectrum in the stratosphere sensed from balloon-borne observations of stellar scintillation", Proc. SPIE 6745, Remote Sensing of Clouds and the Atmosphere XII, 67451K (16 October 2007); doi: 10.1117/12.738176; https://doi.org/10.1117/12.738176

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