Spatial spreading of magnetospherically reflected chorus elements in the inner magnetosphere

Breuillard, H.; Zaliznyak, Yu.; Agapitov, Oleksiy; Artemyev, А. V.; Krasnoselskikh, V.; Rolland, G.

doi:10.5194/angeo-31-1429-2013

Cited by 13 publications

(23 citation statements)

References 50 publications

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“…However, the latter propagate mostly outward (towards higher L, see e.g. Breuillard et al, 2013) thus their normalized frequency is slightly increased (up to ∼ 0.2-0.25 e0 ). Finally, we observe a slow decrease of the peak frequency down to ∼ 0.13 e0 for higher latitudes (λ ≥ 30…”

Section: Discussionmentioning

confidence: 99%

“…This can be explained by the fact that our model does not take into account (see Rönnmark, 1982;Breuillard et al, 2012b, for detailed explanation) the nonlinear mechanism thought to be responsible for chorus wave generation (see e.g. Dysthe, 1971;Omura et al, 1991Omura et al, , 2013Trakhtengerts, 1999;Katoh and Omura, 2007, and references therein).…”

Section: Modelling the Field-aligned Spectral Extent Of Chorus Wavesmentioning

confidence: 99%

“…To simulate the chorus wave power distribution upon frequency along a magnetic field line we use a 3-D ray-tracing code that includes a realistic model of the Earth's inner magnetosphere, described in detail in Breuillard et al (2012b). The magnetic field and thermal plasma densities parameters -e.g.…”

Section: Appendix B: the Earth's Inner Magnetosphere Modelmentioning

confidence: 99%

“…The magnetic field and thermal plasma densities parameters -e.g. MLT = 09:00 and K p = 4, see also Breuillard et al (2012b) for details -are chosen to be typical of the period in which most chorus waves occur in the inner magnetosphere (Agapitov et al, 2011. Ray tracing (here the WHAMP solver) is sensitive to density variations in the chosen model.…”

Section: Appendix B: the Earth's Inner Magnetosphere Modelmentioning

confidence: 99%

“…Making use of the density grids of all particle populations, and implementing their parameters described in the previous paragraph into the WHAMP solver, it is possible to obtain the imaginary part ω of the frequency (i.e. the growth/damping rate γ ) from which one can deduce the amplitude A of the wave (see Breuillard et al, 2012b).…”

Section: Appendix B: the Earth's Inner Magnetosphere Modelmentioning

confidence: 99%

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Field-aligned chorus wave spectral power in Earth's outer radiation belt

Breuillard¹,

Agapitov

Artemyev

et al. 2015

Ann. Geophys.

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Abstract. Chorus-type whistler waves are one of the most intense electromagnetic waves generated naturally in the magnetosphere. These waves have a substantial impact on the radiation belt dynamics as they are thought to contribute to electron acceleration and losses into the ionosphere through resonant wave-particle interaction. Our study is devoted to the determination of chorus wave power distribution on frequency in a wide range of magnetic latitudes, from 0 to 40• . We use 10 years of magnetic and electric field wave power measured by STAFF-SA onboard Cluster spacecraft to model the initial (equatorial) chorus wave spectral power, as well as PEACE and RAPID measurements to model the properties of energetic electrons (∼ 0.1-100 keV) in the outer radiation belt. The dependence of this distribution upon latitude obtained from Cluster STAFF-SA is then consistently reproduced along a certain L-shell range (4 ≤ L ≤ 6.5), employing WHAMP-based ray tracing simulations in hot plasma within a realistic inner magnetospheric model. We show here that, as latitude increases, the chorus peak frequency is globally shifted towards lower frequencies. Making use of our simulations, the peak frequency variations can be explained mostly in terms of wave damping and amplification, but also cross-L propagation. These results are in good agreement with previous studies of chorus wave spectral extent using data from different spacecraft (Cluster, POLAR and THEMIS). The chorus peak frequency variations are then employed to calculate the pitch angle and energy diffusion rates, resulting in more effective pitch angle electron scattering (electron lifetime is halved) but less effective acceleration. These peak frequency parameters can thus be used to improve the accuracy of diffusion coefficient calculations.

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Section: Discussionmentioning

confidence: 99%

Section: Modelling the Field-aligned Spectral Extent Of Chorus Wavesmentioning

confidence: 99%

Section: Appendix B: the Earth's Inner Magnetosphere Modelmentioning

confidence: 99%

Section: Appendix B: the Earth's Inner Magnetosphere Modelmentioning

confidence: 99%

Section: Appendix B: the Earth's Inner Magnetosphere Modelmentioning

confidence: 99%

See 3 more Smart Citations

Field-aligned chorus wave spectral power in Earth's outer radiation belt

Breuillard¹,

Agapitov

Artemyev

et al. 2015

Ann. Geophys.

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Poynting vector and wave vector directions of equatorial chorus

et al. 2016

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We present new results on wave vectors and Poynting vectors of chorus rising and falling tones on the basis of 6 years of THEMIS (Time History of Events and Macroscale Interactions during Substorms) observations. The majority of wave vectors is closely aligned with the direction of the ambient magnetic field (B0). Oblique wave vectors are confined to the magnetic meridional plane, pointing away from Earth. Poynting vectors are found to be almost parallel to B0. We show, for the first time, that slightly oblique Poynting vectors are directed away from Earth for rising tones and toward Earth for falling tones. For the majority of lower band chorus elements, the mutual orientation between Poynting vectors and wave vectors can be explained by whistler mode dispersion in a homogeneous collisionless cold plasma. Upper band chorus seems to require inclusion of collisional processes or taking into account azimuthal anisotropies in the propagation medium. The latitudinal extension of the equatorial source region can be limited to ±6∘ around the B0 minimum or approximately ±5000 km along magnetic field lines. We find increasing Poynting flux and focusing of Poynting vectors on the B0 direction with increasing latitude. Also, wave vectors become most often more field aligned. A smaller group of chorus generated with very oblique wave normals tends to stay close to the whistler mode resonance cone. This suggests that close to the equatorial source region (within ∼20∘ latitude), a wave guidance mechanism is relevant, for example, in ducts of depleted or enhanced plasma density.

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Examining Coherency Scales, Substructure, and Propagation of Whistler Mode Chorus Elements With Magnetospheric Multiscale (MMS)

et al. 2017

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Whistler mode chorus waves are a naturally occurring electromagnetic emission observed in Earth's magnetosphere. Here, for the first time, data from NASA's Magnetospheric Multiscale (MMS) mission were used to analyze chorus waves in detail, including the calculation of chorus wave normal vectors, k. A case study was examined from a period of substorm activity around the time of a conjunction between the MMS constellation and NASA's Van Allen Probes mission on 07 April 2016. Chorus wave activity was simultaneously observed by all six spacecraft over a broad range of L shells (5.5 < L < 8.5), magnetic local time (06:00 < MLT < 09:00), and magnetic latitude (−32° < MLAT < −15°), implying a large chorus active region. Eight chorus elements and their substructure were analyzed in detail with MMS. These chorus elements were all lower band and rising tone emissions, right‐handed and nearly circularly polarized, and propagating away from the magnetic equator when they were observed at MMS (MLAT~−31°). Most of the elements had “hook”‐like signatures on their wave power spectra, characterized by enhanced wave power at flat or falling frequency following the peak, and all the elements exhibited complex and well‐organized substructure observed consistently at all four MMS spacecraft at separations up to 70 km (60 km perpendicular and 38 km parallel to the background magnetic field). The waveforms in field‐aligned coordinates also demonstrated that these waves were all phase coherent, allowing for the direct calculation of k. Error estimates on calculated k revealed that the plane wave approximation was valid for six of the eight elements and most of the subelements. The wave normal vectors were within 20–30° from the direction antiparallel to the background field for all elements and changed from subelement to subelement through at least two of the eight elements. The azimuthal angle of k in the perpendicular plane was oriented earthward and was oblique to that of the Poynting vector, which has implications for the validity of cold plasma theory.

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Spatial spreading of magnetospherically reflected chorus elements in the inner magnetosphere

Cited by 13 publications

References 50 publications

Field-aligned chorus wave spectral power in Earth's outer radiation belt

Field-aligned chorus wave spectral power in Earth's outer radiation belt

Poynting vector and wave vector directions of equatorial chorus

Examining Coherency Scales, Substructure, and Propagation of Whistler Mode Chorus Elements With Magnetospheric Multiscale (MMS)

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