Saitoh Haruhiko, Nishiura Masaki, Kenmochi Naoki, Yoshida Zensho
Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.
National Institute for Fusion Science, Toki, Japan.
Nat Commun. 2024 Feb 15;15(1):861. doi: 10.1038/s41467-024-44977-x.
Wave particle interaction plays an important role in geospace and space weather phenomena. Whistler mode chorus emissions, characterized by non-linear growth and frequency chirping, are common in planetary magnetospheres. They are regarded as the origin of relativistic acceleration of particles in the radiation belts and pulsating aurora. Intensive theoretical investigations and spacecraft observations have revealed several important features of chorus emissions. However, there is a need to conduct high-resolution and reproducible controlled laboratory experiments to deepen the understanding of space weather. Here, we present the spontaneous excitation of chirping whistler waves in hot-electron high-β plasma (β is the ratio of the plasma pressure to the magnetic pressure) in an "artificial magnetosphere", a levitated dipole experiment. These experiments suggest that the generation and nonlinear growth of coherent chorus emissions are ubiquitous in dipole magnetic configuration. We anticipate that these experiments will accelerate the laboratory investigation of space weather phenomena.
波粒相互作用在地球空间和空间天气现象中起着重要作用。以非线性增长和频率啁啾为特征的哨声波合唱辐射在行星磁层中很常见。它们被认为是辐射带中粒子相对论加速和脉动极光的起源。深入的理论研究和航天器观测揭示了合唱辐射的几个重要特征。然而，需要进行高分辨率且可重复的受控实验室实验，以加深对空间天气的理解。在此，我们展示了在一个“人工磁层”（悬浮偶极实验）的热电子高β等离子体（β是等离子体压力与磁压力之比）中啁啾哨声波的自发激发。这些实验表明，相干合唱辐射的产生和非线性增长在偶极磁结构中普遍存在。我们预计这些实验将加速对空间天气现象的实验室研究。
