Abstract Accumulations of ice and dust mixtures may acquire magnetization during deposition in a manner analogous to sedimentary rocks. Here, we consider the process of particles descending through an atmosphere and depositing in a preferential orientation that serves to record the ambient magnetic field during emplacement. We use a simple model for the settling and reorientation of ice particles with magnetic inclusions that includes magnetic torque, aerodynamic forces and gravity, to investigate the parameter space governing the process. For fields in the range of 10's – 100's μ T we find that ice particles of sizes up to ∼100 μ m which contain smaller magnetic grains as nuclei will produce a deposit indeed magnetized in the direction aligned with the applied field, but with a moment that is independent of the field strength. For particles in the 100's μ m range, the magnetic moment increases with the field strength. To demonstrate the effect experimentally, we performed a suite of laboratory deposition simulations followed by measurements of the magnetic moment of the samples. We show that in the idealized laboratory conditions dusty ice magnetizes in the direction of the applied field, with the alignment increasing with its intensity. For the chosen conditions, the magnetization increases rapidly with field intensity in the range 10 – 200 μ T , and approaches a maximal value above that. For a mixture with dust/ice ratio of 5 × 10 − 3 we obtained maximal magnetization values in the range 1.6 × 10 − 5 – 3 × 10 − 3 A m2/kg, depending on the distribution of particle sizes. We show that magnetic particle concentration in the ice determines the level of magnetic remanence, and conclude that the remanent magnetization of natural ice deposit in various settings may be measurable (if unobscured by post-depositional, wind, or other effects) and thus could provide a new paleomagnetic record on Earth and other planetary objects.

中文翻译：

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尘冰沉积物剩磁的实验测定

摘要 冰尘混合物的堆积可能在沉积过程中以类似于沉积岩的方式获得磁化。在这里，我们考虑粒子通过大气下降并以优先方向沉积的过程，该方向用于记录就位期间的环境磁场。我们使用一个简单的模型来沉降和重新定向带有磁性夹杂物的冰粒，包括磁扭矩、空气动力和重力，以研究控制该过程的参数空间。对于 10's – 100's μ T 范围内的场，我们发现大小高达 100 μm 的冰颗粒包含较小的磁性颗粒作为核将产生确实在与外加场对齐的方向上磁化的沉积物，但具有片刻这与场强无关。对于 100 微米范围内的粒子，磁矩​​随场强而增加。为了通过实验证明效果，我们进行了一系列实验室沉积模拟，然后测量样品的磁矩。我们表明，在理想化的实验室条件下，尘冰在外加场的方向上磁化，随着其强度的增加而增加。对于所选条件，磁化强度随场强在 10 – 200 μ T 范围内快速增加，并接近高于该范围的最大值。对于灰尘/冰比为 5 × 10 − 3 的混合物，我们获得了 1.6 × 10 − 5 – 3 × 10 − 3 A m2/kg 范围内的最大磁化值，具体取决于颗粒大小的分布。