Deep Space Exploration Laboratory/School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China.
CAS Center for Excellence in Comparative Planetology/CAS Key Laboratory of Geospace Environment, University of Science and Technology of China, Hefei, China.
Nat Commun. 2023 Jun 6;14(1):3142. doi: 10.1038/s41467-023-38776-z.
Chorus waves are naturally occurring electromagnetic emissions in space and are known to produce highly energetic electrons in the hazardous radiation belt. The characteristic feature of chorus is its fast frequency chirping, whose mechanism remains a long-standing problem. While many theories agree on its nonlinear nature, they differ on whether or how the background magnetic field inhomogeneity plays a key role. Here, using observations of chorus at Mars and Earth, we report direct evidence showing that the chorus chirping rate is consistently related to the background magnetic field inhomogeneity, despite orders of magnitude difference in a key parameter quantifying the inhomogeneity at the two planets. Our results show an extreme test of a recently proposed chorus generation model and confirm the connection between the chirping rate and magnetic field inhomogeneity, opening the door to controlled plasma wave excitation in the laboratory and space.
合唱波是太空中自然产生的电磁发射，已知会在危险的辐射带中产生高能电子。合唱的特征是其快速的频率啁啾，其机制仍然是一个长期存在的问题。虽然许多理论都同意其非线性性质，但它们在背景磁场不均匀性是否以及如何发挥关键作用上存在分歧。在这里，我们利用火星和地球的合唱波观测结果，报告了直接证据，表明尽管两个行星上量化不均匀性的关键参数相差几个数量级，但合唱的啁啾率与背景磁场的不均匀性始终相关。我们的结果对最近提出的合唱波产生模型进行了极端测试，并证实了啁啾率与磁场不均匀性之间的联系，为实验室和空间中的受控等离子体波激发开辟了道路。
