Alfvén Waves Generated Through the Drift‐Bounce Resonant Instability in the Ring Current: A THEMIS Multi‐Spacecraft Case Study

Mager, Olga V.

doi:10.1029/2021ja029241

Cited by 9 publications

(4 citation statements)

References 84 publications

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“…For m < 0, the radial gradient of the distribution function (the second term in Equation 9) causes a drift resonance instability if ∂F/∂L < 0, which was satisfied several times during the observation (Figure 3f). Previous studies have shown that the gradient of the distribution function of ring-current ions can generate poloidal Alfvén waves as well (O. V. Mager, 2021;Mikhailova et al, 2022;Rubtsov et al, 2021;Yamamoto et al, 2019). For a general review of wave-particle interactions, refer to (Klimushkin et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Direct Evidence of Drift‐Compressional Wave Generation in the Earth's Magnetosphere Detected by Arase

Yamamoto,

Rubtsov,

Kostarev

et al. 2024

Geophysical Research Letters

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We present the first direct evidence of an in situ excitation of drift‐compressional waves driven by drift resonance with ring current protons in the magnetosphere. Compressional Pc4–5 waves with frequencies of 4–12 mHz were observed by the Arase satellite near the magnetic equator at L ∼ 6 in the evening sector on 19 November 2018. Estimated azimuthal wave numbers (m) ranged from −100 to −130. The observed frequency was consistent with that calculated using the drift‐compressional mode theory, whereas the plasma anisotropy was too small to excite the drift‐mirror mode. We discovered that the energy source of the wave was a drift resonance instability, which was generated by the negative radial gradient in a proton phase space density at 20–25 keV. This proton distribution is attributed to a temporal variation of the electric field, which formed the observed multiple‐nose structures of ring current protons.

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Section: Discussionmentioning

confidence: 99%

Direct Evidence of Drift‐Compressional Wave Generation in the Earth's Magnetosphere Detected by Arase

Yamamoto,

Rubtsov,

Kostarev

et al. 2024

Geophysical Research Letters

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“…A pp must be higher than 0.5 nT (it corresponds to 0.25 nT wave amplitude) for at least five wave periods in order to distinguish quasi-sinusoidal oscillations from pulses at the same frequency. We chose A pp = 0.5 nT threshold empirically, after comparison with the background noise level and earlier case studies (Mager, 2021;Mikhailova et al, 2022). Usually, quasi-sinusoidal waves have much more oscillation periods, but the wave amplitude gradually increases at the beginning of the observation and gradually decreases at the end.…”

Section: Appendix A: Selection Criteriamentioning

confidence: 99%

Polarization and Spatial Distribution Features of Pc4 and Pc5 Waves in the Magnetosphere

Rubtsov,

Nosé,

Matsuoka

et al. 2023

JGR Space Physics

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Ultra‐low frequency waves interact with different particle populations all over the magnetosphere. Some interaction mechanisms are associated with certain wave modes, but is it really so and what about waves interaction between each other? We present a statistical analysis of Pc4 and Pc5 waves in the magnetosphere of the Earth that were observed by Arase satellite from March 2017 to December 2020. These waves were classified by polarization into toroidal, poloidal, and compressional waves. Toroidal and poloidal waves are thought to be Alfvén waves that are eigenoscillations of Earth’s magnetic field lines. The former are believed to be generated by external sources, while the latter one — by internal sources. We compared spatial distribution features with well‐known case studies to reveal their nature for all three polarizations. A high inclination of Arase orbit supported a wave field‐aligned structure research. We found that toroidal waves are mostly odd harmonics and poloidal waves are both even and odd harmonics of Alfvén waves, while compressional waves were observed in a narrow equatorial region only. Different wave generation mechanisms that cause a clear difference in spatial distributions of toroidal, poloidal, and compressional waves could excite a specific wave polarization. Surprisingly, a statistics of wave polarization has a normal distribution without separate clusters. We suggest that polarization change and mode coupling processes make mixed polarization the most common type of polarization in the magnetosphere. This result raises the question of how the polarization change process affects wave‐particles interactions responsible for energy transport throughout the magnetosphere.

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“…B космической плазме (магнитосферах планет, солнечной хромосфере и короне, межпланетной среде) часто наблюдаются магнитогидродинамические (МГД) волны [Nakariakov et al, 2016]. Как известно, существуют три МГД-моды: альфвеновская, быстрая и медленная магнитозвуковые (БМЗ и ММЗ) [Кадомцев, 1988].…”

Section: Introductionunclassified

Definition of the Alfvén mode in inhomogeneous magnetic field

Klimushkin

Mager

2023

Solnechno-Zemnaya Fizika

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The article is methodological and defines the concept of the linear Alfvén mode. There are two definitions — electrodynamic and hydrodynamic. In the former, the Alfvén mode is considered a wave with a potential transverse electric field. In the latter, waves are more often identified with the Alfvén mode, plasma motion in which is purely vortex. While these definitions are equivalent for homogeneous plasma, they are incompatible if the field line curvature is taken into account: if the transverse electric field is purely potential, the plasma speed has not only a vortex component, but also a potential one, and vice versa. The electrodynamic and hydrodynamic definitions are equivalent only if the wave electric field completely lacks a component along the binormal to the external magnetic field. However, such waves do not exist in nature.

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Alfvén Waves Generated Through the Drift‐Bounce Resonant Instability in the Ring Current: A THEMIS Multi‐Spacecraft Case Study

Abstract: Poloidal Ultra-low-frequency (ULF) Pc4-5 waves (1.7-22 mHz), in which the magnetic field lines oscillate mainly in the radial direction, are regularly recorded both on the daytime and nighttime sides of the magnetosphere (

Cited by 9 publications

References 84 publications

Direct Evidence of Drift‐Compressional Wave Generation in the Earth's Magnetosphere Detected by Arase

Direct Evidence of Drift‐Compressional Wave Generation in the Earth's Magnetosphere Detected by Arase

Polarization and Spatial Distribution Features of Pc4 and Pc5 Waves in the Magnetosphere

Definition of the Alfvén mode in inhomogeneous magnetic field

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