Discovery of proton hill in the phase space during interactions between ions and electromagnetic ion cyclotron waves

AbstractA study using Arase data gives the first observational evidence that the frequency drift of electromagnetic ion cyclotron (EMIC) waves is caused by cyclotron trapping. EMIC emissions play an important role in planetary magnetospheres, causing scattering loss of radiation belt relativistic electrons and energetic protons. EMIC waves frequently show nonlinear signatures that include frequency drift and amplitude enhancements. While nonlinear growth theory has suggested that the frequency change is caused by nonlinear resonant currents owing to cyclotron trapping of the particles, observational evidence for this has been elusive. We survey the wave data observed by Arase from March, 2017 to September 2019, and find the best falling tone emission event, one detected on 11th November, 2017, for the wave particle interaction analysis. Here, we show for the first time direct evidence of the formation of a proton hill in phase space indicating cyclotron trapping. The associated resonance currents and the wave growth of a falling tone EMIC wave are observed coincident with the hill, as theoretically predicted.

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Trapping and amplification of unguided mode EMIC waves in the radiation belt

10.21203/rs.3.rs-132689/v1 ◽

2021 ◽

Author(s):

Geng Wang ◽

Zhonglei Gao ◽

Mingyu Wu ◽

Guoqiang Wang ◽

Sudong Xiao ◽

...

Keyword(s):

Radiation Belt ◽

Abundance Ratio ◽

Relativistic Electrons ◽

Scattering Loss ◽

Propagation Behavior ◽

Guided Mode ◽

Waves Propagation ◽

Spatial Locations ◽

First Time ◽

Emic Waves

Abstract Electromagnetic ion cyclotron (EMIC) waves can cause the scattering loss of the relativistic electrons in the earth's radiation belt. They can be classified into the guided mode and the unguided mode, according to waves propagation behavior. The guided mode waves have been widely investigated in the radiation belt, but the observation of the unguided mode waves have not been expected. Based on the observations of Van Allen Probes, we demonstrate for the first time the existence of the intense unguided mode EMIC waves. The reflection interface formed by the spatial locations of local helium cutoff frequencies can be nearly parallel to the equatorial plane when the proton abundance ratio decreases sharply with L-shell. This structure combined with the anisotropic hot protons can lead to the trapping and significant amplification of the unguided mode waves. These results may help to understand the nature of EMIC waves in the radiation belt.

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Direct Observational Evidence of the Simultaneous Excitation of Electromagnetic Ion Cyclotron Waves and Magnetosonic Waves by an Anisotropic Proton Ring Distribution

10.5194/egusphere-egu21-1492 ◽

2021 ◽

Author(s):

Shangchun Teng ◽

Nigang Liu ◽

Qianli Ma ◽

Xin Tao ◽

Wen Li

Keyword(s):

Energetic Electron ◽

Observational Evidence ◽

Ion Dynamics ◽

Frequency Spectra ◽

Simultaneous Excitation ◽

Proton Distribution ◽

Ion Cyclotron ◽

Electromagnetic Ion Cyclotron Waves ◽

Generation Mechanisms ◽

Emic Waves

<p>Magnetosonic (MS) waves and electromagnetic ion cyclotron (EMIC) waves are two important plasma wave modes in the magnetosphere. Previous simulations have shown that both waves could be generated by a ring-like proton distribution, while direct observational evidence has yet to be reported. Here, we present simultaneous observations of MS and EMIC waves and a detailed case analysis. The linear growth rates estimated for both waves are in good agreement with the observed wave frequency spectra. The measured proton distribution evolution is also compared with the simulation results, providing direct observational evidence for the previous theoretical prediction that anisotropic ring-like proton distributions could excite MS and EMIC waves simultaneously. Our findings are crucial for understanding the generation mechanisms of and relation between MS and EMIC waves and for evaluating their combined effects on energetic electron and ion dynamics.&#160;</p>

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Combined scattering loss of radiation belt relativistic electrons by simultaneous three-band EMIC waves: A case study

Journal of Geophysical Research Space Physics ◽

10.1002/2016ja022483 ◽

2016 ◽

Vol 121 (5) ◽

pp. 4446-4451 ◽

Cited By ~ 11

Author(s):

Fengming He ◽

Xing Cao ◽

Binbin Ni ◽

Zheng Xiang ◽

Chen Zhou ◽

...

Keyword(s):

Radiation Belt ◽

Relativistic Electrons ◽

Scattering Loss ◽

Emic Waves

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Nonlinear Interactions Between Relativistic Electrons and EMIC Waves in Magnetospheric Warm Plasma Environments

Journal of Geophysical Research Space Physics ◽

10.1029/2020ja028089 ◽

2020 ◽

Vol 125 (12) ◽

Author(s):

Jiang Yu ◽

L. Y. Li ◽

Jun Cui ◽

J. B. Cao ◽

Jing Wang ◽

...

Keyword(s):

Relativistic Electrons ◽

Nonlinear Interactions ◽

Warm Plasma ◽

Emic Waves

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Gamma-rays from Solar Flares

Symposium - International Astronomical Union ◽

10.1017/s0074180900162850 ◽

2000 ◽

Vol 195 ◽

pp. 123-132 ◽

Cited By ~ 7

Author(s):

R. Ramaty ◽

N. Mandzhavidze

Keyword(s):

Energy Release ◽

Gamma Rays ◽

Solar Flares ◽

Gamma Ray ◽

Particle Interaction ◽

Mass Motion ◽

Relativistic Electrons ◽

Total Energy Release ◽

Flare Energy ◽

Accelerated Particles

Gamma-ray emission is the most direct diagnostic of energetic ions and relativistic electrons in solar flares. Analysis of solar flare gamma-ray data has shown: (i) ion acceleration is a major consequence of flare energy release, as the total flare energy in accelerated particles appears to be equipartitioned between ≳ 1 MeV/nucleon ions and ≳ 20 keV electrons, and amounts to an important fraction of the total energy release; (ii) there are flares for which over 50% of the energy is in a particles and heavier ions; (iii) in both impulsive and gradual flares, the particles that interact at the Sun and produce gamma rays are essentially always accelerated by the same mechanism that operates in impulsive flares, probably stochastic acceleration through gyroresonant wave particle interaction; and (iv) gamma-ray spectroscopy can provide new information on solar abundances, for example the site of the FIP-bias onset and the photospheric 3He abundance. We propose a new technique for the investigation of mass motion and mixing in the solar atmosphere: the observations of gamma-ray lines from long-term radioactivity produced by flare accelerated particles.

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