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Title: Modulation of chorus intensity by ULF waves deep in the inner magnetosphere

Abstract

Previous studies have shown that chorus wave intensity can be modulated by Pc4-Pc5 compressional ULF waves. In this paper, we present Van Allen Probes observation of ULF wave modulating chorus wave intensity, which occurred deep in the magnetosphere. The ULF wave shows fundamental poloidal mode signature and mirror mode compressional nature. The observed ULF wave can modulate not only the chorus wave intensity but also the distribution of both protons and electrons. Linear growth rate analysis shows consistence with observed chorus intensity variation at low frequency (f <~ 0.3f ce), but cannot account for the observed higher-frequency chorus waves, including the upper band chorus waves. This suggests the chorus waves at higher-frequency ranges require nonlinear mechanisms. Finally, in addition, we use combined observations of Radiation Belt Storm Probes (RBSP) A and B to verify that the ULF wave event is spatially local and does not last long.

Authors:
 [1];  [1];  [2];  [3];  [4];  [5]; ORCiD logo [6]
  1. Univ. of Texas, Dallas, TX (United States). Dept. of Physics
  2. Chinese Academy of Sciences (CAS), Beijing (China). State Key Lab. of Space Weather. National Space Science Center
  3. Aerospace Corporation, El Segundo, CA (United States)
  4. Rice Univ., Houston, TX (United States). Dept. of Physics and Astronomy
  5. New Jersey Inst. of Technology, Newark, NJ (United States)
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Univ. of Texas, Dallas, TX (United States); Rice Univ., Houston, TX (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE; National Science Foundation (NSF); National Aeronautic and Space Administration (NASA)
OSTI Identifier:
1402618
Report Number(s):
LA-UR-16-26169
Journal ID: ISSN 0094-8276; TRN: US1702880
Grant/Contract Number:
AC52-06NA25396; AGS 1405041; NNX15AI93G; NNX14AN55G
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 43; Journal Issue: 18; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; chorus modulation; ULF wave; whistler wave; inner magnetosphere

Citation Formats

Xia, Zhiyang, Chen, Lunjin, Dai, Lei, Claudepierre, Seth G., Chan, Anthony A., Soto-Chavez, A. R., and Reeves, G. D. Modulation of chorus intensity by ULF waves deep in the inner magnetosphere. United States: N. p., 2016. Web. doi:10.1002/2016GL070280.
Xia, Zhiyang, Chen, Lunjin, Dai, Lei, Claudepierre, Seth G., Chan, Anthony A., Soto-Chavez, A. R., & Reeves, G. D. Modulation of chorus intensity by ULF waves deep in the inner magnetosphere. United States. doi:10.1002/2016GL070280.
Xia, Zhiyang, Chen, Lunjin, Dai, Lei, Claudepierre, Seth G., Chan, Anthony A., Soto-Chavez, A. R., and Reeves, G. D. Mon . "Modulation of chorus intensity by ULF waves deep in the inner magnetosphere". United States. doi:10.1002/2016GL070280. https://www.osti.gov/servlets/purl/1402618.
@article{osti_1402618,
title = {Modulation of chorus intensity by ULF waves deep in the inner magnetosphere},
author = {Xia, Zhiyang and Chen, Lunjin and Dai, Lei and Claudepierre, Seth G. and Chan, Anthony A. and Soto-Chavez, A. R. and Reeves, G. D.},
abstractNote = {Previous studies have shown that chorus wave intensity can be modulated by Pc4-Pc5 compressional ULF waves. In this paper, we present Van Allen Probes observation of ULF wave modulating chorus wave intensity, which occurred deep in the magnetosphere. The ULF wave shows fundamental poloidal mode signature and mirror mode compressional nature. The observed ULF wave can modulate not only the chorus wave intensity but also the distribution of both protons and electrons. Linear growth rate analysis shows consistence with observed chorus intensity variation at low frequency (f <~ 0.3fce), but cannot account for the observed higher-frequency chorus waves, including the upper band chorus waves. This suggests the chorus waves at higher-frequency ranges require nonlinear mechanisms. Finally, in addition, we use combined observations of Radiation Belt Storm Probes (RBSP) A and B to verify that the ULF wave event is spatially local and does not last long.},
doi = {10.1002/2016GL070280},
journal = {Geophysical Research Letters},
number = 18,
volume = 43,
place = {United States},
year = {Mon Sep 05 00:00:00 EDT 2016},
month = {Mon Sep 05 00:00:00 EDT 2016}
}

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Cited by: 2works
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  • Theory and observations have linked equatorial VLF waves with pulsating aurora for decades, invoking the process of pitch angle scattering of tens of keV electrons in the equatorial magnetosphere. Recently published satellite studies have strengthened this argument, by showing strong correlation between pulsating auroral patches and both lower-band chorus and tens of keV electron modulation in the vicinity of geosynchronous orbit. Additionally, a previous link has been made between Pc4–5 compressional pulsations and modulation of whistler-mode chorus using Time History of Events and Macroscale Interactions during Substorms. In the current study, we present simultaneous in situ observations of structured chorusmore » waves and an apparent field line resonance (in the Pc4–5 range) as a result of a substorm injection, observed by Van Allen Probes, along with ground-based observations of pulsating aurora. We demonstrate the likely scenario being one of substorm-driven Pc4–5 ULF pulsations modulating chorus waves, and thus providing the driver for pulsating particle precipitation into the Earth's atmosphere. Interestingly, the modulated chorus wave and ULF wave periods are well correlated, with chorus occurring at half the periodicity of the ULF waves. We also show, for the first time, a particular few-Hz modulation of individual chorus elements that coincides with the same modulation in a nearby pulsating aurora patch. As a result, such modulation has been noticed as a high-frequency component in ground-based camera data of pulsating aurora for decades and may be a result of nonlinear chorus wave interactions in the equatorial region.« less
  • The distribution of ULF energy (frequency < 80 mHz) in the inner magnetosphere (L = 2.5-6.5) has been studied using magnetic field measurements made with the Active Magnetospheric Particle Tracers Explorers Charge Composition Explorer (AMPTE CCE) spacecraft during its whole mission of over 4 years. The magnetic field time series was split into consecutive 10-min segments and subjected to fast Fourier transform (FFT), and the spectral data were achieved along with the Kp index and the satellite location. This data base was then used to examine the spatial distribution of ULF energy. Overall, the oscillation energy is localized to themore » dayside except for compressional oscillations associated with substorms. From the spatial distributions of wave power and spectral structures the authors identify several pulsation types, including multiharmonic toroidal oscillations; equatorial compressional Pc 3 oscillations; second harmonic poloidal oscillations; and nightside compressional oscillations; equatorial compressional Pc 3 oscillations; second harmonic poloidal oscillations; and nightside compressional oscillations. The toroidal oscillations are observable even in the plasmasphere, and using their frequencies they can determine the statistical radial profile of the plasma mass density and Alfven velocity. They find a clear signature of the plasmapause in the profiles of these average parameters. Of particular interest among the other oscillation types are the equatorial compressional Pc 3 oscillations that have an average spectral peak around 30 mHz and are present in the prenoon sector and from L{approximately}3 to {approximately}5. The oscillations are similar to the compressional Pc3 previously observed at and near geostationary orbit and might represent magnetohydrodynamic waves propagating from the parallel portion of the bow shock.« less
  • Using high-resolution waveforms measured by the Van Allen Probes, we report a novel observation in the radiation belts. Namely, we show that multiband, discrete, rising-tone whistler-mode chorus emissions exhibit a one-to-one correlation with Langmuir wave bursts. Moreover, the periodic Langmuir wave bursts are generally observed at the phase location where the chorus wave E || component is oriented opposite to its propagation direction. The electron measurements show a beam in phase space density at the particle velocity that matches the parallel phase velocity of the chorus waves. Based on this evidence, we conclude that the chorus waves accelerate the suprathermalmore » electrons via Landau resonance, and generate a localized electron beam in phase space density. Consequently, the Langmuir waves are excited locally and are modulated by the chorus wave phase. As a result, this microscale interaction between chorus waves and high frequency electrostatic waves provides a new insight into the nonlinear wave-particle interaction process.« less
  • The resonance regions for resonant interactions of radiation belt electrons with obliquely propagating whistler-mode chorus waves are investigated in detail in the Dungey magnetic fields that are parameterized by the intensity of uniform southward interplanetary magnetic field (IMF) Bz or, equivalently, by the values of D=(M/B{sub z,0}){sup 1/3} (where M is the magnetic moment of the dipole and B{sub z,0} is the uniform southward IMF normal to the dipole's equatorial plane). Adoption of background magnetic field model can considerably modify the determination of resonance regions. Compared to the results for the case of D = 50 (very close to themore » dipole field), the latitudinal coverage of resonance regions for 200 keV electrons interacting with chorus waves tends to become narrower for smaller D-values, regardless of equatorial pitch angle, resonance harmonics, and wave normal angle. In contrast, resonance regions for 1 MeV electrons tend to have very similar spatial lengths along the field line for various Dungey magnetic field models but cover different magnetic field intervals, indicative of a strong dependence on electron energy. For any given magnetic field line, the resonance regions where chorus-electron resonant interactions can take place rely closely on equatorial pitch angle, resonance harmonics, and kinetic energy. The resonance regions tend to cover broader latitudinal ranges for smaller equatorial pitch angles, higher resonance harmonics, and lower electron energies, consistent with the results in Ni and Summers [Phys. Plasmas 17, 042902, 042903 (2010)]. Calculations of quasi-linear bounce-averaged diffusion coefficients for radiation belt electrons due to nightside chorus waves indicate that the resultant scattering rates differ from using different Dungey magnetic field models, demonstrating a strong dependence of wave-induced electron scattering effect on the adoption of magnetic field model. Our results suggest that resonant wave-particle interaction processes should be implemented into a sophisticated, accurate global magnetic field model to pursue comprehensive and complete models of radiation belt electron dynamics.« less