A Comparison of MGMR3D and CoREAS Simulations for Four-layer Atmospheric Electric Field Structures

Introduction: Radio emissions from extensive air showers can provide valuable insights into the properties of high-energy cosmic rays and the atmospheric conditions through which they propagate. While these emissions can be accurately modeled under fair-weather conditions, the presence of strong and complex atmospheric electric fields during thunderstorms can significantly affect the radio signal. Methods: Measuring these fields directly is challenging due to the instability and unpredictability of thunderclouds, making indirect methods essential. The macroscopic model MGMR3D (Macroscopic GeoMagnetic Radiation, three-dimensional model) offers a semi-analytic approach to reconstructing these atmospheric electric field structures, while the microscopic simulation CoREAS (CORSIKA-based Radio Emission from Air Showers) serves as a detailed benchmark. In this study, the outputs of MGMR3D were validated against CoREAS to assess its ability to reproduce radio emission patterns under multi-layer thunderstorm field configurations. Both models were used to determine the intensity, linear polarization, and circular polarization of radio emissions generated by extensive air showers as they traversed layered electric field structures, including complex four-layer models. Results: The comparison demonstrated that MGMR3D can reliably reproduce the results obtained from CoREAS for both simple electric field configurations as well as intricate four-layer structures. The good agreement between both models indicates that MGMR3D captures the essential physics governing radio emission in strong electric field conditions. Conclusion: The findings demonstrate that MGMR3D, through its optimization procedure, is an efficient tool for reconstructing the internal electric field structures of thunderclouds; consequently, the model is suitable for extracting detailed electric field profiles from experimental radio measurements. This represents an important step in the use of radio detection as a diagnostic tool for atmospheric electricity during thunderstorms.