格陵兰萨米特站辐射冰介电测量
Radiofrequency Ice Dielectric Measurements at Summit Station, Greenland
摘要：
我们最近报告了格陵兰Summit站冷极地冰的射频衰减长度，基于2021年夏季对射频基岩回波强度的双基地雷达测量。这些数据还包括归因于冰盖（层）内分层杂质或介电不连续性的回波，这使得可以研究a）估计相干（离散层，例如）与不连贯（例如，散装体积）散射，b）内层反射系数的大小，c）反射的方位角不对称性（双折射）的限制，以及d）在~100 MHz带宽上的信号色散的限制。我们发现，i）在平均10000次回波触发后，在热地板上可观察到反射信号（到大约1500 m的深度）与完全相干一致，ii）在大约-60到-70 dB处测量内层反射系数，iii）垂直传播信号的双折射效应相对于在南极进行的可比研究小一个数量级，和iv）在我们的实验范围内，冰川冰在中微子探测实验相关的频带上是非色散的。
英文摘要：
We recently reported on the radio-frequency attenuation length of cold polar ice at Summit Station, Greenland, based on bistatic radar measurements of radio-frequency bedrock echo strengths taken during the summer of 2021. Those data also include echoes attributed to stratified impurities or dielectric discontinuities within the ice sheet (layers), which allow studies of a) estimation of the relative contribution of coherent (discrete layers, e.g.) vs. incoherent (bulk volumetric, e.g.) scattering, b) the magnitude of internal layer reflection coefficients, c) limits on the azimuthal asymmetry of reflections (birefringence), and d) limits on signal dispersion in-ice over a bandwidth of ~100 MHz. We find that i) after averaging 10000 echo triggers, reflected signal observable over the thermal floor (to depths of approximately 1500 m) are consistent with being entirely coherent, ii) internal layer reflection coefficients are measured at approximately -60 to -70 dB, iii) birefringent effects for vertically propagating signals are smaller by an order of magnitude relative to comparable studies performed at South Pole, and iv) within our experimental limits, glacial ice is non-dispersive over the frequency band relevant for neutrino detection experiments.
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