Statistical study of ULF waves in the magnetotail by THEMIS 
observations

Zhang, Shuai; Tian, Anmin; Shi, Quanqi; Li, Hanlin; Degeling, A. W.; Rae, I. J.; Forsyth, C.; Zong, Qiugang; Wang, Mengmeng; Shen, Xiaochen; Sun, W.; Bai, Shaochun; Guo, Ruilong; Wang, Huizi; Fazakerly, Andrew; Fu, S. Y.; Pu, Zuiyin

doi:10.5194/angeo-2018-39

Cited by 3 publications

(4 citation statements)

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“…Furthermore, in Figure 3e, it can be seen that the compressional component shows enhanced power closer to the magnetopause but is generally weaker than the other two components in the inner magnetosphere, except for L ∼ 5–7 in the dayside region, where the radial component is the weakest. The enhanced nightside power that is observed primarily in the radial but also in the azimuthal components can be attributed to magnetotail flapping and dynamic processes during substorm activity, which are well‐known causes of enhanced ULF wave power in the magnetotail, both at the Earth and other planetary magnetospheres (e.g., Olson, 1999; Sun et al., 2015; Zhang et al., 2018). The results of the distribution of wave power in MLT are further discussed in the following section.…”

Section: Statistical Distribution Of Ulf Wave Powermentioning

confidence: 99%

Distribution of ULF Wave Power in Magnetic Latitude and Local Time Using THEMIS and Arase Measurements

Sarris

Zhao

et al. 2022

JGR Space Physics

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Magnetospheric ultra-low-frequency (ULF) waves are fluctuations in the mHz to Hz range of frequencies in the electric and magnetic fields that are everlasting and ubiquitous within the Earth's magnetosphere. They are known to play a key role in shaping and altering energetic particle populations in the radiation belts (see, e.g., reviews by W. Li & Hudson, 2019;X. Li & Temerin, 2001; and references therein). In particular, fluctuations in the Pc4 and Pc5 ranges of frequencies (6.7-22.2 mHz and 1.7-6.7 mHz, respectively; Jacobs et al., 1964) overlap with the drift frequencies of energetic (hundreds of keV to a few MeV) electrons and have been associated both with auroral processes such as the pulsating aurora (see, e.g., Motoba et al., 2018) and with enhanced radial diffusion, one of the established mechanisms controlling the variability of energetic electrons in the radiation belts

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Section: Statistical Distribution Of Ulf Wave Powermentioning

confidence: 99%

Distribution of ULF Wave Power in Magnetic Latitude and Local Time Using THEMIS and Arase Measurements

Sarris

Zhao

et al. 2022

JGR Space Physics

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“…Alfvénic standing waves are characterized by a 90° phase difference between the electric field and magnetic field components (e.g., Singer et al, ). The sign of phase delay can be used to diagnose the harmonics mode of Pc4‐5 ULF waves; for instance, the poloidal mode could be second harmonic (fundamental) wave if the phase of the radial magnetic field Br leads (lags) the azimuthal electric field Ea by 90°, if measured slightly south of the magnetic equator (e.g., Hao et al, ; Liu et al, ; Takahashi et al, , ; Zhang et al, ). For poloidal mode waves, the second harmonic mode is the most common phenomenon in the Earth's magnetosphere, which is usually observed on the duskside near L ~ 5–6 with frequency in Pc4 band (6.7–22.2 mHz; e.g., Dai et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…According to whether the magnetic field perturbations are in the radial or azimuthal directions, they are classified as toroidal or poloidal mode. Pc4‐5 toroidal waves with low m are usually considered to be caused by external sources, such as Kelvin‐Helmholtz instability along the magnetopause (e.g., Claudepierre et al, ; Ling et al, ; Rae et al, ; Zhang et al, ), solar wind dynamic pressure impulse (e.g., Allan et al, ; Degeling et al, ; Lee & Lysak, ; Shen et al, , ; Shi et al, , ; Tian et al, ; Zong et al, ), and foreshock transients (e.g., Hartinger et al, ; Shen et al, ). Pc4‐5 poloidal waves with high wave number are usually driven by localized kinetic plasma instabilities such as the drift‐bounce resonance instability (e.g., Oimatsu et al, ; Southwood, ; Yang et al, ), the free energy could be generally provided by bump‐on‐tail distribution at low‐energy (~1–10 keV; e.g., Liu et al, ; Shi et al, ; Takahashi et al, ) or inward gradient of ion phase space density (PSD) at high energy (tens to hundreds of keV; e.g., Dai et al, ; Min et al, ; Yamamoto et al, ).…”

Section: Introductionmentioning

confidence: 99%

Pc4‐5 Poloidal ULF Wave Observed in the Dawnside Plasmaspheric Plume

et al. 2019

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A localized Pc4-5 ultralow-frequency (ULF) wave event associated with a plasmaspheric plume was observed by THEMIS-E on the dawnside near L = 6, which was identified as a second harmonic poloidal wave. The plume was identified as a sudden density enhancement during an outbound pass. The charged particle populations in the plume have a variety of periodic modulation characteristics at different energies. First, there is an antiphase relationship between magnetic field Br and particle flux across a wide energy range both for ions and electrons (~50 keV to 1 MeV). Second, there is a 180°phase shift in the modulated ion flux within an energy range of~2-6 keV, with negative slope dispersions of ion pitch angle distributions at~2-6 keV and~50-75 keV, which are characteristic of drift-bounce resonances. Third, the lower-energy (<32 eV) ion flux is modulated at double the wave frequency, which are the result of E × B effect. Considering the generation mechanism of this poloidal mode wave within the plume, we find that it is likely generated by drift-bounce resonance from an unstable population of ions, due to an inward radial phase space density gradient. We suggest that the localization of waves to the plume is because the high plasma density reduces the local poloidal mode eigenfrequency, enabling a match to the drift-bounce frequencies of these ions, and resonant energy transfer from these particles to the eigenfunction at this location. This generates the Pc4-5 second harmonic poloidal waves at a much lower L region than would otherwise be expected. Key Points:• The high-m poloidal waves in the dawnside plume were observed by THEMIS-E • The inward radial gradient of~57 keV and higher plasma density enable the second harmonic poloidal wave to occur in the dawnside plume • Three types of particle flux modulations are observed simultaneously along with the wave in different energy bands Supporting Information:• Supporting Information S1

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“…Alfvén waves, which were first predicted by Alfvén (1942), widely exist in various regions of the terrestrial magnetosphere, such as the tail lobes (Keiling et al., 2005; Takada et al., 2006), plasma sheet boundary layer (PSBL; Dombeck et al., 2005; Wygant et al., 2000), plasma sheet (Ergun et al., 2014), auroral region (Knudsen et al., 1992; Park et al., 2017), and inner magnetosphere (Chen et al., 2018; Osaki et al., 1998). Their frequencies in the magnetosphere are on the order of mHz, which are in the ultra‐low frequency (ULF) range (Keiling, 2009; Zhang et al., 2018). These Alfvén waves can carry significant electromagnetic energy from remote (Keiling, 2009), and play an important role in magnetospheric dynamics, such as field‐aligned currents (FACs; Kepko et al., 2014; Wang et al., 2021), auroral accelerations (Hasegawa, 1976; Schroeder et al., 2021), and radiation belt dynamics (Elkington et al., 2003; Zong et al., 2009).…”

Section: Introductionmentioning

confidence: 99%

Evidence of Alfvén Waves Generated by Mode Coupling in the Magnetotail Lobe

Sun

Wang

Zhang

et al. 2021

Geophysical Research Letters

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Numerous satellite observations have shown that the rapid enhancement of the nightside FACs constituting the substorm current wedge is carried by Alfvén waves (Baumjohann & Glassmeier, 1984;Kepko et al., 2014). In the context of auroral accelerations, electrons can be accelerated by Alfvén waves above the auroral acceleration region along magnetic field lines (Wygant et al., 2002). Recent experiments on the Large Plasma Device further demonstrated a clear causal relationship between Alfvén waves and accelerated electrons that cause auroras (Schroeder et al., 2021). In addition, some Alfvén waves have a frequency comparable to the drift frequency of the radiation belt electrons, which allows the resonant interaction between them, leading to the acceleration of those energetic electrons in the radiation belt (Elkington et al., 2003;Zong et al., 2009).Various candidate mechanisms have been proposed for the excitation of Alfvén waves in the magnetosphere (Keiling, 2009), such as solar wind perturbations (Claudepierre et al., 2010) and Kelvin-Helmholtz instabilities (KHIs; C. Wang et al., 2013). The generation mechanisms depend on the region where they operate (C. Wang

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Statistical study of ULF waves in the magnetotail by THEMIS observations

Abstract: Abstract. Ultra-low frequency (ULF) waves are ubiquitous in the magnetosphere. Previous studies mostly focused on ULF waves in the dayside or near-earth region (with radial distance R

Cited by 3 publications

References 5 publications

Distribution of ULF Wave Power in Magnetic Latitude and Local Time Using THEMIS and Arase Measurements

Distribution of ULF Wave Power in Magnetic Latitude and Local Time Using THEMIS and Arase Measurements

Pc4‐5 Poloidal ULF Wave Observed in the Dawnside Plasmaspheric Plume

Evidence of Alfvén Waves Generated by Mode Coupling in the Magnetotail Lobe

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