Formation of energetic electron butterfly distributions by magnetosonic waves via Landau resonance

Li, Jinxing; Ni, Binbin; Ma, Q.; Xie, Luhua; Pu, Z. Y.; Fu, S. Y.; Thorne, R. M.; Bortnik, J.; Chen, Lunjin; Li, Wen; Baker, D. N.; Kletzing, C.; Kurth, W. S.; Hospodarsky, G. B.; Fennell, J. F.; Reeves, G. D.; Spence, H. E.; Funsten, H. O.; Summers, Danny

doi:10.1002/2016gl067853

Cited by 91 publications

(131 citation statements)

References 42 publications

(54 reference statements)

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“…These PADs are usually seen at higher L shells and are associated with drift shell splitting [ Stone , ]. Current speculation attributes these PADs to interaction with equatorial magnetosonic waves [ Li et al , ], although recent work by Albert et al [] has shown that cross diffusion due to hiss and lightening generated whistlers may also explain the observations.…”

Section: Discussionmentioning

confidence: 99%

Prompt acceleration of magnetospheric electrons to ultrarelativistic energies by the 17 March 2015 interplanetary shock

et al. 2016

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Trapped electrons in Earth's outer Van Allen radiation belt are influenced profoundly by solar phenomena such as high‐speed solar wind streams, coronal mass ejections (CME), and interplanetary (IP) shocks. In particular, strong IP shocks compress the magnetosphere suddenly and result in rapid energization of electrons within minutes. It is believed that the electric fields induced by the rapid change in the geomagnetic field are responsible for the energization. During the latter part of March 2015, a CME impact led to the most powerful geomagnetic storm (minimum Dst = −223 nT at 17 March, 23 UT) observed not only during the Van Allen Probe era but also the entire preceding decade. Magnetospheric response in the outer radiation belt eventually resulted in elevated levels of energized electrons. The CME itself was preceded by a strong IP shock whose immediate effects vis‐a‐vis electron energization were observed by sensors on board the Van Allen Probes. The comprehensive and high‐quality data from the Van Allen Probes enable the determination of the location of the electron injection, timescales, and spectral aspects of the energized electrons. The observations clearly show that ultrarelativistic electrons with energies E > 6 MeV were injected deep into the magnetosphere at L ≈ 3 within about 2 min of the shock impact. However, electrons in the energy range of ≈250 keV to ≈900 keV showed no immediate response to the IP shock. Electric and magnetic fields resulting from the shock‐driven compression complete the comprehensive set of observations that provide a full description of the near‐instantaneous electron energization.

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Section: Discussionmentioning

confidence: 99%

Prompt acceleration of magnetospheric electrons to ultrarelativistic energies by the 17 March 2015 interplanetary shock

et al. 2016

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“…These waves are important as they can accelerate electrons up to MeV energies and help form the outer radiation [Horne et al, 2007]. More recently, magnetosonic waves have been observed on the inner edge of the outer radiation belt and may be associated with butterfly-type electron distributions [Li et al, 2016], although this is controversial [Albert et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

Propagation and linear mode conversion of magnetosonic and electromagnetic ion cyclotron waves in the radiation belts

Horne

Miyoshi

2016

Geophysical Research Letters

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Magnetosonic waves and electromagnetic ion cyclotron (EMIC) waves are important for electron acceleration and loss from the radiation belts. It is generally understood that these waves are generated by unstable ion distributions that form during geomagnetically disturbed times. Here we show that magnetosonic waves could be a source of EMIC waves as a result of propagation and a process of linear mode conversion. The converse is also possible. We present ray tracing to show how magnetosonic (EMIC) waves launched with large (small) wave normal angles can reach a location where the wave normal angle is zero and the wave frequency equals the so‐called crossover frequency whereupon energy can be converted from one mode to another without attenuation. While EMIC waves could be a source of magnetosonic waves below the crossover frequency, magnetosonic waves could be a source of hydrogen band waves but not helium band waves.

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“…The drift‐averaged amplitude of these MS waves at the equator of L = 2.4 is B w = 350 pT (Li, Ni, et al, ), estimated from the multipoint measurements by the Van Allen Probes and THEMIS satellites (Angelopoulos, ), and the latitudinal distribution takes the form of

B^{w} ((), λ) = B^{w} exp ((), - λ^{2} / λ_{w}^{2})

where the latitudinal extent is λ w = 5. 4 ° .…”

Section: Observations and Modelsmentioning

confidence: 99%

“…Three physical mechanisms have been proposed for the interaction between MS waves and energetic electrons: Landau resonance (Horne et al, ), transit‐time scattering (Bortnik & Thorne, ; Li et al, ), and bounce resonance (Chen et al, ; Li, Ni, et al, ; Shprits, ). Landau resonance occurs when the electron velocity along the magnetic field ( v ∥ ) equal to the wave parallel phase velocity ( ω / k ∥ ).…”

Section: Introductionmentioning

confidence: 99%

The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

Lei

Xie

et al. 2017

JGR Space Physics

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Magnetosonic (MS) waves have been found capable of creating radiation belt electron butterfly distributions in the inner magnetosphere. To investigate the physical nature of the interactions between radiation belt electrons and MS waves, and to explore a preferential condition for MS waves to scatter electrons efficiently, we performed a comprehensive parametric study of MS wave‐electron interactions using test particle simulations. The diffusion coefficients simulated by varying the MS wave frequency show that the scattering effect of MS waves is frequency insensitive at low harmonics (f < 20 fcp), which has great implications on modeling the electron scattering caused by MS waves with harmonic structures. The electron scattering caused by MS waves is very sensitive to wave normal angles, and MS waves with off 90° wave normal angles scatter electrons more efficiently. By simulating the diffusion coefficients and the electron phase space density evolution at different L shells under different plasma environment circumstances, we find that MS waves can readily produce electron butterfly distributions in the inner part of the plasmasphere where the ratio of electron plasma‐to‐gyrofrequency (fpe/fce) is large, while they may essentially form a two‐peak distribution outside the plasmapause and in the inner radiation belt where fpe/fce is small.

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Formation of energetic electron butterfly distributions by magnetosonic waves via Landau resonance

Cited by 91 publications

References 42 publications

Prompt acceleration of magnetospheric electrons to ultrarelativistic energies by the 17 March 2015 interplanetary shock

Prompt acceleration of magnetospheric electrons to ultrarelativistic energies by the 17 March 2015 interplanetary shock

Propagation and linear mode conversion of magnetosonic and electromagnetic ion cyclotron waves in the radiation belts

The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

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