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Found 5 entries in the Bibliography.
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2019 
Effect of LowHarmonic Magnetosonic Waves on the Radiation Belt Electrons Inside the Plasmasphere In this paper, we presented two observational cases and simulations to indicate the relationship between the formation of butterflylike electron pitch angle distributions and the emission of lowharmonic (LH) fast magnetosonic (MS) waves inside the highdensity plasmasphere. In the wave emission region, the pitch angle of relativistic (>1 MeV) electrons becomes obvious butterflylike distributions for both events (nearequatorially mirroring electrons are transported to lower pitch angles). Unlike relativistic (>1 MeV) electrons, energetic electrons (<1 MeV) change slightly, except that relatively lowenergy electrons (<~150 keV) show butterflylike distributions in the 21 August 2013 event. In theory, the LH MS waves can affect differentenergy electrons through the bounce resonance, Landau resonance, and transit time scattering. By performing the FokkerPlanck diffusion simulations, we demonstrate that the bounce resonance with the LH MS waves mainly leads to the butterfly pitch angle distribution of MeV electrons, whereas the Landau resonance and transit time scattering mainly affect energetic electrons in the highdensity region. Yu, J.; Li, L; Cui, J.; Cao, J.; Wang, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2019 YEAR: 2019 DOI: 10.1029/2018JA026328 bounce resonance; Electron acceleration; Landau resonance; magnetosonic waves; transittime scattering; Van Allen Probes 
EMIC WaveDriven Bounce Resonance Scattering of Energetic Electrons in the Inner Magnetosphere While electromagnetic ion cyclotron (EMIC) waves have been long studied as a scattering mechanism for ultrarelativistic (megaelectron volt) electrons via cyclotronresonant interactions, these waves are also of the right frequency to resonate with the bounce motion of lowerenergy (approximately tens to hundreds of kiloelectron volts) electrons. Here we investigate the effectiveness of this bounce resonance interaction to better determine the effects of EMIC waves on subrelativistic electron populations in Earth\textquoterights inner magnetosphere. Using wave and plasma parameters directly measured by the Van Allen Probes, we estimate bounce resonance diffusion coefficients for four different events, illustrative of wave and plasma parameters to be encountered in the inner magnetosphere. The range of electron energies and pitch angles affected is examined to better assess the realistic effects of EMICdriven bounce resonance on energetic electron populations based on actual, locally observed eventbased parameters. Significant local diffusion coefficients (~ > 106 s1) for 50 to 100keV electrons are achieved for both H+ band wave events as well as He+ band, with diffusion coefficients peaking for near90\textdegree pitch angles but remaining elevated for intermediate ones as well. Diffusion coefficients for higherenergy 200keV electrons are typically multiple orders of magnitude lower (ranging from 1011 to 106 s1) and often peak at lower pitch angles (~20\textendash30\textdegree). These results suggest that both H+ and He+ band EMIC waves can play a role in shaping lowerenergy electron dynamics via bounceresonant interactions, in addition to their role in relativistic electron loss via cyclotron resonance. Blum, L.W.; Artemyev, A.; Agapitov, O.; Mourenas, D.; Boardsen, S.; Schiller, Q.; Published by: Journal of Geophysical Research: Space Physics Published on: 03/2019 YEAR: 2019 DOI: 10.1029/2018JA026427 bounce resonance; EMIC wave; energetic electrons; Radiation belts; Van Allen Probes 
2017 
Ring Current HeIon Control by Bounce Resonant ULF Waves Ring current energy Heion (\~65 keV to \~520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (\~9 hours) of the spacecraft and is observed to be \~50\textendash100\% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of 10\textquoterights of sec. These periods correspond to the bounce resonant timescales of the ring current Heions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately two years) shows that the wave and Heion flux variations are generally anticorrelated, suggesting the bounce resonant pitchangle scattering process as a major component in the scattering of Heions. Kim, Hyomin; Gerrard, Andrew; Lanzerotti, Louis; SotoChavez, Rualdo; Cohen, Ross; Manweiler, Jerry; Published by: Journal of Geophysical Research: Space Physics Published on: 09/2017 YEAR: 2017 DOI: 10.1002/2017JA023958 bounce resonance; Helium ion; ring current; ULF waves; Van Allen Probes 
Bounceresonant interactions with magnetospheric waves have been proposed as important contributing mechanisms for scattering nearequatorially mirroring electrons by violating the second adiabatic invariant associated with the electron bounce motion along a geomagnetic field line. This study demonstrates that lowfrequency plasmaspheric hiss with significant wave power below 100 Hz can bounceresonate efficiently with radiation belt electrons. By performing quantitative calculations of pitchangle scattering rates, we show that lowfrequency hiss induced bounceresonant scattering of electrons has a strong dependence on equatorial pitchangle αeq. For electrons with αeq close to 90\textdegree, the timescale associated with bounce resonance scattering can be comparable to or even less than 1 hour. Cyclotron and Landauresonant interactions between lowfrequency hiss and electrons are also investigated for comparisons. It is found that while the bounce and Landau resonances are responsible for the diffusive transport of nearequatorially mirroring electrons to lower αeq, pitchangle scattering by cyclotron resonance could take over to further diffuse electrons into the atmosphere. Bounce resonance provides a more efficient pitchangle scattering mechanism of relativistic (>= 1 MeV) electrons than Landau resonance due to the stronger scattering rates and broader resonance coverage of αeq, thereby demonstrating that bounce resonance scattering by lowfrequency hiss can contribute importantly to the evolution of the electron pitchangle distribution and the loss of radiation belt electrons. Cao, Xing; Ni, Binbin; Summers, Danny; Zou, Zhengyang; Fu, Song; Zhang, Wenxun; Published by: Geophysical Research Letters Published on: 09/2017 YEAR: 2017 DOI: 10.1002/2017GL075104 bounce resonance; Lowfrequency hiss; Radiation Belt Dynamics; Van Allen Probes; waveparticle interactions 
2015 
Nonlinear Bounce Resonances between Magnetosonic Waves and Equatorially Mirroring Electrons Equatorially mirroring energetic electrons pose an interesting scientific problem, since they generally cannot resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Observationally it is well known that the fluxof these equatorial particles does not simply continue to build up indefinitely, and so a mechanism must necessarily exist that transports these particles from a equatorial pitch angle of 90 degrees down to lower values. However this mechanism has not been uniquely identified yet. Here, we investigate the mechanism of bounce resonance with equatorial noise (or fast magnetosonic waves). A test particle simulation is used to examine the effects of monochromatic magnetosonic waves on the equatorially mirroring energetic electrons, with a special interest in characterizing the effectiveness of bounce resonances. Our analysis shows that bounce resonances can occur at the first three harmonics of the bounce frequency (nωb, n = 1 , 2, and 3 ) and can effectively reduce the equatorial pitch angle to values where resonant scattering by whistlermode waves becomes possible. We demonstrate that the nature of bounce resonance is nonlinear and we propose a nonlinear oscillation model for characterizing bounce resonances using two key parameters, effective wave amplitude \~A and normalized wave number inline image. The threshold for higher harmonic resonance is more strict, favoring higher \~A and inline image and the change in equatorial pitch angle is strongly controlled by inline image. We also investigate the dependence of bounce resonance effects on various physical parameters, including wave amplitude, frequency, wave normal angle and initial phase, plasmadensity, and electron energy. It is found that the effect of bounce resonance is sensitive to the wave normal angle. We suggest that the bounce resonant interaction might lead to an observed pitch angle distribution with a minimum at 90o. Chen, Lunjin; Maldonado, Armando; Bortnik, Jacob; Thorne, Richard; Li, Jinxing; Dai, Lei; Zhan, Xiaoya; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2015 YEAR: 2015 DOI: 10.1002/2015JA021174 bounce resonance; equatorioal noise; magnetosonic waves; nonlinear; Radiation belt; wave particle interaction 
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