Radiation Field Inside the Homogeneous Moon Excited by a Vertical Magnetic Dipole

The investigation of radiation field in the moon is important for the moon subsurface detection and vertical magnetic dipoles (VMD) are especially useful as sources and probes. The present work focuses on the radiation field inside the moon excited by a VMD located on or near the moon’s surface. Analytical expressions are derived with approximate method. Contributions of the fields come from two parts: the series expansions of low-order terms using the multiplication iteration method, and the integrals of high-order terms using the asymptotic method. Meanwhile, the field of high-order terms is close to the total field. Compared with the calculation’s direct sum, our method has advantages of accuracy and is suitable for the large-size model. For a source-receiver system on or near the homogeneous moon, it is found the waves propagating inside the moon can be described in terms of ray optics. Based on the formulas, various modes of reflection are taken into account, and the intensity of the primarily reflected waves is calculated numerically. Furthermore, effects of propagation distance and angel, the operating frequency, as well as the height of the source are considered to demonstrate the properties of the field. Particularly, the proposed method and formulas have applications to the moon interior exploration.