Plasmasphere Control of ULF Wave Distribution at Different Geomagnetic Conditions

Rubtsov, A. V.; Nosé, M.; Matsuoka, A.; Kasahara, Y.; Kumamoto, A.; Tsuchiya, F.; Shinohara, I.; Miyoshi, Y.

doi:10.1029/2023ja031675

“…Sarris et al (2022) did not investigate solar wind and geomagnetic conditions, although we studied their distributions . Moreover, in a companion paper (Rubtsov et al, 2023), we display ULF wave distributions at different conditions and its dependence on the plasmapause location. Wave events method allowed to investigate wave frequency distribution (see Figures 3, 5, and 8).…”

Section: Comparison With Previous Studiesmentioning

confidence: 99%

“…Our paper is aimed to fill these gaps. Geomagnetic conditions and plasmasphere boundary influence on spatial distribution of Pc4 and Pc5 waves is shown in a companion paper (Rubtsov et al, 2023).…”

mentioning

confidence: 99%

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

Rubtsov,

Nosé,

Matsuoka

et al. 2023

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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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Polarization distribution of transverse ULF waves according to Van Allen Probe A data: whether toroidal and poloidal waves exist separately in the magnetosphere?

Yakimchuk,

Rubtsov,

Klimushkin

2023

Solar-Terrestrial Physics

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Ultralow-frequency (ULF) waves play an important role in energy transfer within Earth's magnetosphere due to intensive interaction with the surrounding plasma. Previous works have assumed that these waves are strictly divided by polarization into toroidal, when the magnetic field oscillates in the azimuthal direction, and poloidal, when it oscillates in the radial direction. The former are azimuthally large-scale and are excited by external sources, whereas the latter are small-scale and are generated by internal plasma instabilities. Observations show, however, that waves of mixed polarization often occur, and the nature of this mixing has not been explained. In this paper, we carry out a statistical study and show that the polarization of transverse waves has a normal distribution, and the maximum corresponds to oscillations of the toroidal and poloidal components with the same amplitude. At the same time, the spatial distributions of toroidal and poloidal waves are clearly different, but only lead to a small shift in the position of the distribution maximum. This result suggests that in order to compare the theory with ULF wave observations it is necessary to take into account the processes of polarization change, which can affect wave-particle interactions in the magnetosphere.

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Polarization distribution of transverse ULF waves according to Van Allen Probe A data: whether toroidal and poloidal waves exist separately in the magnetosphere?

Yakimchuk,

Rubtsov,

Klimushkin

2023

Solnechno-Zemnaya Fizika

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0

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Ultralow-frequency (ULF) waves play an important role in energy transfer within Earth's magnetosphere due to intensive interaction with the surrounding plasma. Previous works have assumed that these waves are strictly divided by polarization into toroidal, when the magnetic field oscillates in the azimuthal direction, and poloidal, when it oscillates in the radial direction. The former are azimuthally large-scale and are excited by external sources, whereas the latter are small-scale and are generated by internal plasma instabilities. Observations show, however, that waves of mixed polarization often occur, and the nature of this mixing has not been explained. In this paper, we carry out a statistical study and show that the polarization of transverse waves has a normal distribution, and the maximum corresponds to oscillations of the toroidal and poloidal components with the same amplitude. At the same time, the spatial distributions of toroidal and poloidal waves are clearly different, but only lead to a small shift in the position of the distribution maximum. This result suggests that in order to compare the theory with ULF wave observations it is necessary to take into account the processes of polarization change, which can affect wave-particle interactions in the magnetosphere.

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Plasmasphere Control of ULF Wave Distribution at Different Geomagnetic Conditions

Cited by 4 publications

References 123 publications

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

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

Polarization distribution of transverse ULF waves according to Van Allen Probe A data: whether toroidal and poloidal waves exist separately in the magnetosphere?

Polarization distribution of transverse ULF waves according to Van Allen Probe A data: whether toroidal and poloidal waves exist separately in the magnetosphere?

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