Eastward Propagating Second Harmonic Poloidal Waves Triggered by Temporary Outward Gradient of Proton Phase Space Density: Van Allen Probe A Observation

Yamamoto, Kazuhiro; Nosé, M.; Keika, K.; Hartley, D. P.; Smith, C. W.; MacDowall, R. J.; Lanzerotti, L. J.; Mitchell, D. G.; Reeves, G. D.; Wygant, J. R.; Bonnell, J. W.; Oimatsu, S.

doi:10.1029/2019ja027158

Cited by 24 publications

(37 citation statements)

References 74 publications

(127 reference statements)

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“…The drift-bounce resonance condition ( r = m d +N b ) suggests that protons of 17.4 keV would experience an drift-bounce resonance (with N = 1) with the waves at intermediate pitch angles, ∼ 40 • and 140 • , if the waves have an m of ∼200 as suggested by Yamamoto et al, (2019; see Figure S2a and b). According to the conventional theory (e.g., Zhu et al, 2020), a 180 • phase shift is expected across either of the resonant pitch angles.…”

Section: Observationsmentioning

confidence: 90%

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Pitch Angle Structures of Ring Current Ions Induced by Evolving Poloidal Ultra‐Low Frequency Waves

Liu

Zong

Zhou

et al. 2020

Geophysical Research Letters

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Ultra‐low frequency (ULF) waves can effectively accelerate ring current ions through drift‐bounce resonance. Conventional theories have been developed to understand this resonance since the dawn of the space age, which usually assume ULF waves are quasi‐steady in time. However, ULF waves would experience growth and damping stages in the real magnetosphere, which requires an adjustment of the conventional theories. Here, we attempt to reveal how ions respond to evolving ULF waves. By analyzing an event observed by Van Allen Probe A and reproducing the observations via simulation, we find the phase shift of ion flux oscillation across resonant pitch angles varies with time, when wave growth and damping cannot be neglected. As a result, the inclination angle of stripes in pitch angle spectrogram varies with time, causing “fishbone‐like” pitch angle structures. One should take into account such ion behaviors when considering the role of drift‐bounce resonance in the real magnetosphere.

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Section: Observationsmentioning

confidence: 90%

“…Therefore, this set of wave parameters are reasonable. The wave number m is chosen as 170, in the m range suggested by Yamamoto et al (2019). As suggested by Figure S2a The simulation results are shown in the right column of Figure 3.…”

Section: Simulation and Interpretationmentioning

confidence: 99%

Pitch Angle Structures of Ring Current Ions Induced by Evolving Poloidal Ultra‐Low Frequency Waves

Liu

Zong

Zhou

et al. 2020

Geophysical Research Letters

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“…There have been a number of observational studies discussing the drift‐bounce resonance excitation of internally driven ULF waves. While there have been several studies which observed fundamental poloidal waves associated with the drift resonance (e.g., Dai et al, 2013; Yamamoto et al, 2018), previous observations overwhelmed the drift‐bounce resonance excitation of second harmonic poloidal waves (e.g., Le et al, 2017; Min et al, 2017; Oimatsu et al, 2018; Takahashi et al, 1985, 2018; Yamamoto et al, 2019). These observations suggest that internally driven ULF waves excited by the drift‐bounce resonance tend to have a poloidal polarization and propagate westward with high m numbers (| m | ~ 70–200) (e.g., Dai et al, 2013; Takahashi et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Excitation of Internally Driven ULF Waves by the Drift‐Bounce Resonance With Ring Current Ions Based on the Drift‐Kinetic Simulation

et al. 2020

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We investigated the excitation mechanism and global distribution of internally driven Pc3-Pc5 ultralow-frequency waves in the inner magnetosphere using a kinetic and self-consistent simulation (Geospace Environment Modeling System for Integrated Studies-Ring Current model). These waves can be excited through the drift-bounce resonance with ring current ions injected into the inner magnetosphere during substorms. Initial phase space density of ring current ions is the butterfly-like distribution with the asymmetry in pitch angle direction. We find two kinds of internally driven ultralow-frequency waves. First, the dynamic power spectra of the field fluctuations show the excitation of poloidal, toroidal, and compressional Pc5 waves. We find that the excited waves are fundamental modes propagating westward with the azimuthal wave number of m~− 50. These waves are excited by the drift resonance with ions having the energy of 50-150 keV. Second, we can reproduce the excitation of poloidal Pc3 waves in the dusk region with m~− 30, which are driven by the bounce resonance with ions having energies of 20-50 keV for the first time. We investigate the energy transfer between ions and waves and find that poloidal Pc5 and Pc3 waves are excited mainly by positive energy gradient of the phase space density, while we find the inward gradient of the phase space density at L > 6. The velocity distribution of the growth rate suggests that Pc5 waves are driven by ions with pitch angle of around 90°, while Pc3 waves are excited by ions at oblique pitch angle.

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“…One candidate for this interaction is ultra-low frequency (ULF) wave-particle interaction. Previous studies have proved that drift-bounce resonance, a primary type of ULF wave-particle interaction, can efficiently realize the energy exchange between waves and particles (e.g., Oimatsu et al, 2018Oimatsu et al, , 2020Ren et al, 2015Ren et al, , 2016Ren et al, , 2019Southwood & Kivelson, 1981Yamamoto et al, 2019;Yang et al, 2010;Zong et al, 2007Zong et al, , 2009Zong, Wang, et al, 2017). According to Southwood and Kivelson (1981), drift-bounce resonance occurs when the following condition is satisfied:  is particle bounce-averaged drift frequency, and b E  is particle bounce frequency.…”

Section: Introductionmentioning

confidence: 99%

Off‐Equatorial Minima Effects on ULF Wave‐Ion Interaction in the Dayside Outer Magnetosphere

Liu

Zong

et al. 2021

Geophysical Research Letters

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The ultra-low frequency wave-particle drift-bounce resonance in the inner magnetosphere has been studied in detail, due to its important role in particle energization. However, it remains an open question how drift-bounce resonance manifests in the dayside outer magnetosphere, where particles' orbits show bifurcations because of off-equatorial magnetic field minima. In this study, we investigate this question, by analyzing Magnetospheric Multiscale observations of the January 20, 2017 event. A testparticle simulation is conducted to help us understand the observations. The observed pitch angle-time spectrograms show "pawtrack-like" structures. We find there are more than two resonant pitch angles at fixed energy, since off-equatorial minima change the relationship between the bounce (drift) frequency and pitch angle from unimodal function to trimodal function. These results reveal a new drift-bounce acceleration mechanism in the dayside outer magnetosphere, which potentially affects the efficiency of particle energization during geomagnetic activities like geomagnetic storms. Plain Language SummaryThe sun continuously ejects ionized gases called solar winds toward the Earth, affecting Earth's geomagnetic field. When the solar activity is strong, the geomagnetic field is severely disturbed, influencing the safety of power transmissions and space activities. This phenomenon is connected with particle acceleration in the geomagnetic field. The low frequency oscillation of geomagnetic field lines could efficiently transfer energy to charged particles in space, which plays an important role in particle acceleration. This study analyzes special observations which are different from the conventional pattern. A simulation is conducted to help interpret the observations. We find this low frequency magnetic field oscillation interacts with particles differently near the dayside boundary of the geomagnetic field, as the compression of the geomagnetic field by solar winds affects the motion of charged particles nearby. These results help us better understand the formation of geomagnetic activities.LI ET AL.

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Eastward Propagating Second Harmonic Poloidal Waves Triggered by Temporary Outward Gradient of Proton Phase Space Density: Van Allen Probe A Observation

Cited by 24 publications

References 74 publications

Pitch Angle Structures of Ring Current Ions Induced by Evolving Poloidal Ultra‐Low Frequency Waves

Pitch Angle Structures of Ring Current Ions Induced by Evolving Poloidal Ultra‐Low Frequency Waves

Excitation of Internally Driven ULF Waves by the Drift‐Bounce Resonance With Ring Current Ions Based on the Drift‐Kinetic Simulation

Off‐Equatorial Minima Effects on ULF Wave‐Ion Interaction in the Dayside Outer Magnetosphere

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