Measurements and modeling of near-surface radio propagation in glacial ice and implications for neutrino experiments
Measurements and modeling of near-surface radio propagation in glacial ice and implications for neutrino experiments
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DOI：
10.1103/physrevd.98.043010
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发表时间：
2018-08-13
影响因子：
5
通讯作者：
Saltzberg, D.
中科院分区：
文献类型：
--
作者：
Deaconu, C.;Vieregg, A. G.;Saltzberg, D.
我们目前的无线电传输测量在类似的100 MHz的范围内通过类似的100米深的区域下面的表面的冰在首脑会议站，格陵兰岛，称为积雪。在积雪中，折射率的变化是由于从表面的雪到下面的冰川冰的过渡，影响了无线电信号在该地区的传播。我们比较我们的观察到的时域有限差分（FDTD）电磁波模拟，它支持存在三类传播：散装传播射线弯曲模式，导致所谓的“阴影”区域的某些几何形状的传输，由冰/空气界面引起的表面波模式，和任意深度的水平传播模式，需要从一个光滑的密度梯度扰动。在非阴影区，我们的测量是一致的批量传播射线弯曲模式在时间和幅度。我们还观察到在阴影区域的信号，在冲突与批量传播的射线弯曲模型，但与FDTD模拟使用各种积雪模型首脑会议站一致。我们在所有几何形状下测量的幅度和时间与FDTD模拟的预测一致。在阴影区域中，所观察到的信号的幅度与从体传播模式到表面或水平传播模式的2.4%（功率为0.06%）或更小的最佳拟合耦合分数值一致。这两个区域中可观测信号的相对幅度对于旨在检测来自冰川冰中相互作用的天体物理高能中微子的无线电发射的实验非常重要，这些实验依赖于无线电传播模型来通知模拟和执行事件重建。
We present measurements of radio transmission in the similar to 100 MHz range through a similar to 100 m deep region below the surface of the ice at Summit Station, Greenland, called the firn. In the firn, the index of refraction changes due to the transition from snow at the surface to glacial ice below, affecting the propagation of radio signals in that region. We compare our observations to a finite-difference time-domain (FDTD) electromagnetic wave simulation, which supports the existence of three classes of propagation: a bulk propagation ray-bending mode that leads to so-called "shadowed" regions for certain geometries of transmission, a surface-wave mode induced by the ice/air interface, and an arbitrary-depth horizontal propagation mode that requires perturbations from a smooth density gradient. In the non-shadowed region, our measurements are consistent with the bulk propagation ray-bending mode both in timing and in amplitude. We also observe signals in the shadowed region, in conflict with a bulk-propagation-only ray-bending model, but consistent with FDTD simulations using a variety of firn models for Summit Station. The amplitude and timing of our measurements in all geometries are consistent with the predictions from FDTD simulations. In the shadowed region, the amplitude of the observed signals is consistent with a best-fit coupling fraction value of 2.4% (0.06% in power) or less to a surface or horizontal propagation mode from the bulk propagation mode. The relative amplitude of observable signals in the two regions is important for experiments that aim to detect radio emission from astrophysical high-energy neutrinos interacting in glacial ice, which rely on a radio propagation model to inform simulations and perform event reconstruction.