Effect of Low‐Harmonic Magnetosonic Waves on the Radiation Belt Electrons Inside the Plasmasphere

Yu, Jiahong; Li, L. Y.; Cui, Jun; Cao, Jinbin; Wang, J.

doi:10.1029/2018ja026328

Cited by 30 publications

(33 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The electron butterfly pitch angle distribution (PAD), which is defined as the distribution with peak flux off 90° pitch angle, has been a research hotspot in the community of magnetospheric physics during the Van Allen Probes era (e.g., Hua et al, ; Li et al, ; Li et al, ; Li et al, ; Maldonado et al, ; Ni et al, ; Xiao et al, ; Yu et al, ; Zhao, Li, Blake, Fennell, Claudepierre, Baker, Jaynes, & Malaspina, , Zhao, Li, Blake, Fennell, Claudepierre, Baker, Jaynes, Malaspina, & Kanekal, ). The butterfly PAD observed at a certain location can provide clues about what specific physic processes have taken place there, and they may improve the understanding of the dynamics of the radiation belts.…”

Section: Introductionmentioning

confidence: 99%

Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events

Xiong

Xie

et al. 2019

Geophysical Research Letters

View full text Add to dashboard Cite

The magnetic dips can create the electron butterfly pitch angle distribution (PAD) in the inner magnetosphere. However, its universality is still unconfirmed. We statistically investigate the global distribution of the occurrence rate of the magnetic dip-related butterfly PAD for 466 keV and 2.1 MeV electrons using the measurements of the twin Van Allen Probes spanning from September 2012 to November 2018. The statistical results show that the magnetic dip-related butterfly PADs are mainly confined to duskside to midnight within 4.5 < L < 6, and the peak occurrence rate (30% for 466 KeV and 70% for 2.1 MeV) occurs at the duskside equator around L = 5. The parametric study results suggest that the butterfly PADs preferably occur for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with the statistic results. This work confirms the vital importance of the magnetic dips on the evolution of the electron PADs.Plain Language Summary A previous case study has shown that small localized depression of the background magnetic field can lead to the formation of butterfly pitch angle distribution (PAD) of the energetic electrons in the outer radiation belt. We present a statistical study to investigate the occurrence rate of the electron butterfly PAD with magnetic field depression at different locations in the near-Earth space. The statistical result shows that the magnetic field depression-related electron butterfly PAD preferably takes place at duskside equator with altitude~4 Earth radius at which the occurrence rate reaches 30% for low energy electrons (~400 keV) and 70% for high energy electrons (~2 MeV). We also apply a parametric study to understand in detail how the electron butterfly PAD is created by magnetic field depression and the result suggests that the butterfly PAD preferably occurs for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with Van Allen Probe observations. The results of this paper have confirmed the generality of the magnetic field depression-related electron butterfly PAD in the inner magnetosphere and improved the understating of the influence of magnetic field variation on electron PAD in the space environment.Key Points:• The occurrence rate of bz dip-related electron butterfly PADs peaks (30% for 466 keV and 70% for 2.1 MeV) at duskside equator around L = 5 • Bz dip events are common at night side and duskside within L = 4-6 and the depth of bz dips peaks (~10%) around L = 5 at MLT = 18 • Butterfly PADs preferably occur for electron with large negative radial flux gradient and isotropic initial PAD in large bz dip at high L Supporting Information:• Supporting Information S1

show abstract

Section: Introductionmentioning

confidence: 99%

Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events

Xiong

Xie

et al. 2019

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…According to previous studies (e.g. Horne et al, ; Yu J et al, ), the tangent of the wave normal angle ( X = tan θ ) is assumed to be a Gaussian distribution

\begin{matrix} alignleft \\ align-1 g (x) = \exp [- {(\frac{X - X_{m}}{X_{w}})}^{2}], X_{\min} < X < X_{\max} & align-2 \end{matrix}

with peak at X m = tan 89°, half‐width X w = tan 86°, and lower and upper cutoffs X min = X m − X w and X max = X m + X w . Following previous studies (Lyons, ; Glauert and Horne, ), the bounce‐averaged diffusion coefficients in a dipole field can be written as:

\begin{matrix} alignleft \\ align-1 ⟨D_{α α}⟩ = \frac{1}{T (α_{eq})} \int_{0}^{λ_{m}} D_{α α} \frac{\cos α}{co s^{2} α_{eq}} co s^{7} λ d λ, & align-2 \end{matrix}

\begin{matrix} alignleft \\ align-1 ⟨D_{α p}⟩ = \frac{1}{T (α_{eq})} \int_{0}^{λ_{m}} D_{α p} \frac{co s^{4} λ {(1 + 3 co s^{2} λ)}^{1 / 4}}{\cos α_{eq}} d λ<...> \end{matrix}

…”

Section: Proton Scattering Ratesmentioning

confidence: 99%

“…According to previous studies (e.g. Horne et al, 2007;Yu J et al, 2019), the tangent of the wave normal angle (X = tan θ) is assumed to be a Gaussian distribution…”

Section: Figures 2c and 2dmentioning

confidence: 99%

Ring current proton scattering by low-frequency magnetosonic waves

Wang

Cui

2019

Earth and Planetary Physics

View full text Add to dashboard Cite

Magnetosonic (MS) waves are believed to have the ability to affect the dynamics of ring current protons both inside and outside the plasmasphere. However, previous studies have focused primarily on the effect of high‐frequency MS waves (f > 20 Hz) on ring current protons. In this study, we investigate interactions between ring current protons and low‐frequency MS waves (< 20 Hz) inside the plasmasphere. We find that low‐frequency MS waves can effectively accelerate < 20 keV ring current protons on time scales from several hours to a day, and their scattering efficiency is comparable to that due to high‐frequency MS waves (>20 Hz), from which we infer that omitting the effect of low‐frequency MS waves will considerably underestimate proton depletion at middle pitch angles and proton enhancement at large pitch angles. Therefore, ring current proton modeling should take into account the effects of both low‐ and high‐frequency MS waves.

show abstract

“…It is found that when the transit‐time scattering is considered, the interaction range of particle pitch angles and energies could become much broader (see Figure S1 in the supporting information for more detailed description), as compared to the quasilinear resonant theory (Bortnik & Thorne, 2010; Lei et al, 2017). Generally, one uses test particle simulations to investigate this well‐known effect (Li et al, 2014; Yu et al, 2019), and it usually costs a large amount of computation resources to obtain a diffusion coefficient map but gives a poor insight into the dominant physical processes of wave‐particle interactions. Alternatively, Bortnik et al (2015) provided an analytical approximation which can capture the main results of test particle simulations but take a computation time about 4 order of magnitude faster than the latter.…”

Section: Introductionmentioning

confidence: 99%

Revisit the Analytical Approximation of Transit‐Time Scattering for Fast Magnetosonic Waves

Yuan

2020

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

Nonresonant interactions between fast magnetosonic waves and magnetospheric particles have obtained more and more attention. Through such nonresonant interactions, magnetosonic waves can lead to the so‐called transit‐time scattering on particles. The previous analytical approximation has been demonstrated capable of capturing the main results of test particle simulations but takes a computation time about 4 order of magnitude faster than the latter. However, the typical ripples in the diffusion coefficient maps are usually left out. In this paper, we have first discussed the reason for the lack of these typical ripples produced by previous analytical approximation. Then the previous algorithm has been modified to be capable of producing typical ripples in the electron diffusion coefficient maps. Our new analytical expression can be applied to wave models with a Gaussian distribution or a rectangular distribution in wave amplitude. Finally, it is shown that the modified algorithm can be also applied to ring current protons.

show abstract

Effect of Low‐Harmonic Magnetosonic Waves on the Radiation Belt Electrons Inside the Plasmasphere

Cited by 30 publications

References 53 publications

Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events

Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events

Ring current proton scattering by low-frequency magnetosonic waves

Revisit the Analytical Approximation of Transit‐Time Scattering for Fast Magnetosonic Waves

Contact Info

Product

Resources

About