“Zipper‐like” periodic magnetosonic waves: Van Allen Probes, THEMIS, and magnetospheric multiscale observations

Li, J.; Bortnik, J.; Li, W.; Thorne, R. M.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Wygant, J. R.; Breneman, A. W.; Thaller, S. A.; Funsten, H. O.; Mitchell, D. G.; Manweiler, J. W.; Torbert, R. B.; Contel, O. Le; Ergun, R. E.; Lindqvist, Per‐Arne; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C. T.

doi:10.1002/2016ja023536

Cited by 12 publications

(15 citation statements)

References 67 publications

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“…further investigated high-resolution Cluster Wideband Data for all 17 events where these were available, and they revealed the presence of a harmonic line structure in all of them. The emissions may occasionally consist of two frequency bands of interleaved QP elements (Li et al, 2017) and were also observed at altitudes as low as 700 km .…”

Section: 1029/2018ja025382mentioning

confidence: 97%

Detailed Properties of Equatorial Noise With Quasiperiodic Modulation

et al. 2018

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Equatorial noise (EN) emissions are electromagnetic waves observed routinely in the equatorial region of the inner magnetosphere. Although they are typically continuous in time, they sometimes exhibit a quasiperiodic (QP) time modulation of the wave intensity, with modulation periods on the order of minutes. We perform a detailed analysis of 118 EN events with the QP modulation. The events are observed preferentially outside the plasmasphere. We determine the times and frequencies of individual QP elements forming the events. Apart from the event modulation period, this allows us to characterize the intensity and the frequency drift of individual QP wave elements. It is shown that the element intensity peaks at the magnetic equator. The modulation period within a single event is usually quite stable, with variations lower than 25% of the median value in the vast majority of cases. The events with shorter modulation periods are typically more intense, and they tend to have larger frequency drifts. These relations resemble the relations formerly revealed for extra low frequency/very low frequency quasiperiodic emissions, suggesting that the origin of the QP modulation of the wave intensity of EN and ELF/VLF emissions might be similar.

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Section: 1029/2018ja025382mentioning

confidence: 97%

Detailed Properties of Equatorial Noise With Quasiperiodic Modulation

et al. 2018

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“…Besides, radial and azimuthal propagation, combined with wave trapping by density gradients, may account for the origin of some of the wave occurrence inside the plasmapause, which otherwise could not be explained by the local excitation mechanism (Ma, Li, Chen, Thorne, & Angelopoulos, 2014;Ma, Li, Chen, Thorne, Kletzing, et al, 2014). In addition, recent observations show a short-timescale (∼minute) quasi-periodicity of wave amplitude with a frequencytime dispersion (similar to chorus chirps) (Boardsen et al, 2014;Fu, Cao, et al, 2014;Li et al, 2017;Němec, Santolík, Hrbáčková, Pickett, & Cornilleau-Wehrlin, 2015;Walker et al, 2016), whose cause is still unclear. Fast magnetosonic waves can interact with the local radiation belt electron population resonantly and nonresonantly, efficiently accelerating some particles to high energies while scattering others into the loss cone (e.g., Albert et al, 2016;Artemyev et al, 2015;Bortnik et al, 2015;Chen et al, 2015;Horne et al, 2007;Li et al, 2014Li et al, , 2015Li et al, , 2016Maldonado et al, 2016;Ma et al, 2016;Mourenas et al, 2013;Ni et al, 2017;Shprits, 2016;Shprits et al, 2013;Tao & Li, 2016;Yang et al, 2014;.…”

Section: Introductionmentioning

confidence: 99%

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

et al. 2018

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Linear Vlasov theory and particle‐in‐cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to have larger ∂fp/∂v⊥ under the assumption that the observed distribution corresponds to a marginally stable state when the distribution has already been scattered by the excited waves. The results show that the positive slope is the source of the proton cyclotron harmonic waves at propagation quasi‐perpendicular to the background magnetic field, and as a result of interactions with the excited waves the evolving proton distribution progresses approximately toward the observed distribution.

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“…Triggered by the ring distribution of energetic protons, MS waves are initially excited with very oblique wave normal angles and then propagate in both radial and azimuthal directions that are nearly perpendicular to the background magnetic field (e.g., Chen et al, 2011;. Recent observations also reported that, besides the frequently present harmonic structures (e.g., Balikhin et al, 2015), MS waves occasionally consist of discrete wave elements with the rising tone (e.g., Boardsen et al, 2014;Fu et al, 2014) and "zipper-like" periodic structures (Li et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Resonant Scattering of Radiation Belt Electrons by Off‐Equatorial Magnetosonic Waves

Zou

et al. 2018

Geophysical Research Letters

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Fast magnetosonic (MS) waves are commonly regarded as electromagnetic waves that are characteristically confined within ±3° of the geomagnetic equator. We report two typical off‐equatorial MS events observed by Van Allen Probes, that is, the 8 May 2014 event that occurred at the geomagnetic latitudes of 7.5°–9.2° both inside and outside the plasmasphere with the wave amplitude up to 590 pT and the 9 January 2014 event that occurred at the latitudes of—(15.7°–17.5°) outside the plasmasphere with a smaller amplitude about 81 pT. Detailed test particle simulations quantify the electron resonant scattering rates by the off‐equatorial MS waves to find that they can cause the pitch angle scattering and momentum diffusion of radiation belt electrons with equatorial pitch angles < ~75° or < ~58° (depending on the wave latitudinal coverage) on timescales of a day. Subsequent two‐dimensional Fokker‐Planck diffusion simulations indicate that the strong off‐equatorial MS waves are capable of efficiently transporting high pitch angle electrons to lower pitch angles to facilitate the formation of radiation belt electron butterfly distributions for a broad energy range from ~100 keV to >1 MeV within an hour. Our study clearly demonstrates that the presence of off‐equatorial MS waves, in addition to equatorial MS waves, can contribute importantly to the dynamical variations of radiation belt electron fluxes and their pitch angle distribution.

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“Zipper‐like” periodic magnetosonic waves: Van Allen Probes, THEMIS, and magnetospheric multiscale observations

Cited by 12 publications

References 67 publications

Detailed Properties of Equatorial Noise With Quasiperiodic Modulation

Detailed Properties of Equatorial Noise With Quasiperiodic Modulation

Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism

Resonant Scattering of Radiation Belt Electrons by Off‐Equatorial Magnetosonic Waves

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