Particle-sounding of the spatial structure of kinetic Alfvén waves

• Published in: Nature communications Vol. 14; no. 1; p. 2088
• Main Authors: Liu, Z.-Y., Zong, Q.-G., Rankin, R., Zhang, H., Hao, Y.-X., He, J.-S., Fu, S.-Y., Wu, H.-H., Yue, C., Pollock, C. J., Le, G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.04.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/33/525/869; 639/766/525/869; 704/525/869; Charged particles; Electric currents; Electromagnetic fields; Energy dissipation; Humanities and Social Sciences; Interstellar matter; Laboratories; Magnetic fields; Magnetohydrodynamic waves; multidisciplinary; Physics; Planetary magnetospheres; Plasma; Protons; Science; Science (multidisciplinary); Sounding; Space plasmas; Stellar coronas; Thermal energy; Upper bounds; Wavelength; Waves
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-37881-3

Kinetic Alfvén waves (KAWs) are ubiquitous throughout the plasma universe. Although they are broadly believed to provide a potential approach for energy exchange between electromagnetic fields and plasma particles, neither the detail nor the efficiency of the interactions has been well-determined yet. The primary difficulty has been the paucity of knowledge of KAWs’ spatial structure in observation. Here, we apply a particle-sounding technique to Magnetospheric Multiscale mission data to quantitatively determine the perpendicular wavelength of KAWs from ion gyrophase-distribution observations. Our results show that KAWs’ perpendicular wavelength is statistically 2.4 ± 0.7 times proton thermal gyro-radius. This observation yields an upper bound of the energy the majority proton population can reach in coherent interactions with KAWs, that is, roughly 5.76 times proton perpendicular thermal energy. Therefore, the method and results shown here provide a basis for unraveling the effects of KAWs in dissipating energy and accelerating particles in a number of astrophysical systems, e.g., planetary magnetosphere, astrophysical shocks, stellar corona and wind, and the interstellar medium. Kinetic Alfven Waves (KAWs) are ubiquitous in space plasmas. Here, the authors show that application of particle sounding technique to Magnetospheric Multiscale Mission data enables measuring perpendicular wavelength of KAWs.