Low-frequency Whistler Waves Modulate Electrons and Generate Higher-frequency Whistler Waves in the Solar Wind

Abstract The role of whistler-mode waves in the solar wind and the relationship between their electromagnetic fields and charged particles is a fundamental question in space physics. Using high-temporal-resolution electromagnetic field and plasma data from the Magnetospheric MultiScale spacecraft, w...

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Bibliographic Details
Published in:The Astrophysical journal 2021-12, Vol.923 (2), p.216
Main Authors: Yao, S. T., Shi, Q. Q., Zong, Q. G., Degeling, A. W., Guo, R. L., Li, L., Li, J. X., Tian, A. M., Zhang, H., Yao, Z. H., Fu, H. S., Liu, C. M., Sun, W. J., Niu, Z., Li, W. Y., Liu, Z. Y., Le Contel, O., Zhang, S., Xiao, C., Shang, W. S., Torbert, R. B., Ergun, R. E., Lindqvist, P.-A., Pollock, C. J.
Format: Article
Language:English
Subjects:
Astrophysics
Charged particles
Earth and Planetary Astrophysics
Electric currents
Electromagnetic fields
Electromagnetism
Electron energy
Energy conversion
Interplanetary magnetic fields
Magnetic fields
Magnetic mirrors
Magnetohydrodynamics
Magnetospheres
Particle interactions
Physics
Pitch (inclination)
Solar energy
Solar wind
Solar wind velocity
Solar-terrestrial interactions
Space plasmas
Spacecraft
Valleys
Wave generation
Whistler waves
Whistlers
Wind speed
Wind velocities
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Summary:Abstract The role of whistler-mode waves in the solar wind and the relationship between their electromagnetic fields and charged particles is a fundamental question in space physics. Using high-temporal-resolution electromagnetic field and plasma data from the Magnetospheric MultiScale spacecraft, we report observations of low-frequency whistler waves and associated electromagnetic fields and particle behavior in the Earth’s foreshock. The frequency of these whistler waves is close to half the lower-hybrid frequency (∼2 Hz), with their wavelength close to the ion gyroradius. The electron bulk flows are strongly modulated by these waves, with a modulation amplitude comparable to the solar wind velocity. At such a spatial scale, the electron flows are forcibly separated from the ion flows by the waves, resulting in strong electric currents and anisotropic ion distributions. Furthermore, we find that the low-frequency whistler wave propagates obliquely to the background magnetic field ( B 0 ), and results in spatially periodic magnetic gradients in the direction parallel to B 0 . Under such conditions, large pitch-angle electrons are trapped in wave magnetic valleys by the magnetic mirror force, and may provide free perpendicular electron energy to excite higher-frequency whistler waves. This study offers important clues and new insights into wave–particle interactions, wave generation, and microscale energy conversion processes in the solar wind.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/ac2e97