对称非球形冰晶对太赫兹波的衰减效应

Nonspherical symmetric ice crystal attenuation for terahertz wave

水汽凝结体对太赫兹波在大气中的传输衰减起重要作用。结合T-matrix方法,数值模拟了云层中非球形冰晶在太赫兹波段的吸收和散射效应,建立了对称性非球形冰晶的太赫兹波衰减统计模型。分析了不同结构的非球形冰晶的消光特性,对比MPM模型的球形水云衰减,结果显示太赫兹波段对称非球形冰晶的散射特性明显,衰减效应强于球形水滴,衰减系数平均为20 d B左右,1 THz以上消光截面随冰晶形状的变化而变化,为太赫兹星地通信提供了参考数据。

Significant research efforts have been carried out so far to develop models for the prediction of cloud effects on earth-space links in terahertz frequency.A statistic attenuation model for terahertz wave is presented with T-matrix method of nonspherical symmetric ice crystal.The scattering and absorption coefficients are calculated and analyzed on the basis of the microphysical data.By using the results of highly accurate T-matrix computations for circular cylinder particles with varying degrees of diameter-to-length ratios,the effects of a deviation of ice crystal shapes for terahertz wave are analyzed.Our results imply that numerical averaging of extinction characteristics of real cloud ice crystal over sizes may rely on a significantly coarser size-parameter resolution.