Microburst precipitation of energetic electrons associated with chorus wave generation

Hikishima, Mitsuru; Omura, Yoshiharu; Summers, Danny

doi:10.1029/2010gl042678

Cited by 90 publications

(105 citation statements)

References 14 publications

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“…Omura et al (2008Omura et al ( , 2009) describe the detailed nonlinear dynamics of cyclotron-resonant electrons and postulate the formation of electromagnetic electron "holes" that result in resonant currents generating rising-tone emissions. Various aspects of this nonlinear theory have been verified by sophisticated full-scale simulations of the generation and growth of whistler-mode chorus elements by Omura et al (2008Omura et al ( , 2009, Hikishima et al (2009) ;Hikishima et al (2010) and Katoh and Omura (2011). Summers et al (2012b) …”

Section: Introductionmentioning

confidence: 99%

“…Relativistic (∼ MeV) electrons can be generated in the outer radiation belt due to cyclotron resonance with chorus (Summers et al, 1998(Summers et al, , 2002(Summers et al, , 2007aRoth et al, 1999;Meredith et al, 2003;Summers and Omura, 2007;Xiao et al, 2010;Su et al, 2014). Chorus waves can pitch-angle scatter outer zone electrons into the loss cone and induce particle loss to the atmosphere (Lorentzen et al, 2001;O'Brien et al, 2004;Thorne et al, 2005;Summers et al, 2007a, b;Ni et al, 2008;Hikishima et al, 2010). Whistler-mode waves are instrumental in limiting stably trapped electron fluxes in planetary radiation belts (Kennel and Petschek, 1966;Summers et al, 2009Summers et al, , 2011Mauk and Fox, 2010;Tang and Summers, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Effects of cold electron number density variation on whistler-mode wave growth

2014

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Abstract. We examine how the growth of magnetospheric whistler-mode waves depends on the cold (background) electron number density N 0 . The analysis is carried out by varying the cold-plasma parameter a = (electron gyrofrequency) 2 /(electron plasma frequency) 2 which is proportional to 1/N 0 . For given values of the thermal anisotropy A T and the ratio N h /N 0 , where N h is the hot (energetic) electron number density, we find that, as N 0 decreases, the maximum values of the linear and nonlinear growth rates decrease and the threshold wave amplitude for nonlinear growth increases. Generally, as N 0 decreases, the region of (N h /N 0 , A T )-parameter space in which nonlinear wave growth can occur becomes more limited; that is, as N 0 decreases, the parameter region permitting nonlinear wave growth shifts to the top right of (N h /N 0 , A T ) space characterized by larger N h /N 0 values and larger A T values. The results have implications for choosing input parameters for full-scale particle simulations and also in the analysis of whistler-mode chorus data.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of cold electron number density variation on whistler-mode wave growth

2014

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“…They have been intensively studied up to now (see, e.g., comprehensive reviews by Sazhin and Hayakawa, 1992;Trakhtengerts and Rycroft, 2008, and references therein), because they are critical to electron acceleration and losses (Summers et al, 2002;Horne et al, 2005;Summers et al, 2007;Shprits et al, 2008;Hikishima et al, 2010;Santolík et al, 2010), which define the Earth's radiation belt dynamics (Lyons and Thorne, 1973). Magnetospheric chorus waves typically appear as short coherent wave bursts propagating in the non-ducted whistler mode in two distinct frequency bands, scaling on the equatorial electron gyrofrequency e,eq .…”

Section: Introductionmentioning

confidence: 99%

Spatial spreading of magnetospherically reflected chorus elements in the inner magnetosphere

Breuillard¹,

Zaliznyak

Agapitov

et al. 2013

Ann. Geophys.

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Abstract. Chorus-type whistler waves are known to be generated in the vicinity of the magnetic equator, in the low-density plasma trough region. These wave packets propagate towards the magnetic poles, deviating from the magnetic field lines, before being eventually reflected at higher latitudes. Magnetospheric reflection of whistler waves results in bounce oscillations of these waves through the equator. Our study is devoted to the problem of geometrical spreading of these whistler-mode waves after their first magnetospheric reflection, which is crucial to determine where wave–particle interactions occur. Recently, experimental studies stated that the relative intensity of the reflected signal was generally between 0.005 and 0.05 of the source signal. We model such wave packets by means of ray tracing technique, using a warm plasma dispersion function along their trajectory and a realistic model of the inner magnetosphere. We reproduce the topology of the reflected energy distribution in the equatorial plane by modeling discrete chorus elements generated at the equator. Our calculations show that the spatial spreading is large and strongly dependent upon initial wave parameters, especially the chorus wave frequency. Thus, the divergence of each element ray trajectories can result in the filling of a large region (about 4 Earth radii around the source) of the magnetosphere and a reflected intensity of 0.005–0.06 of the source signal in the equatorial plane. These results are in good agreement with previous Cluster and THEMIS observations.

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“…being diffusive or nonlinear, is also undergoing intense debate and research (Albert, 2002;Bortnik et al, 2008;Hikishima et al, 2010;Yoon, 2011;Tao et al, 2012Tao et al, , 2013Tao et al, , 2014a.…”

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confidence: 99%

A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

Teng¹,

Tao²,

Li³

et al. 2018

Preprint

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Abstract. Spatial distribution and source region size of chorus waves are important parameters in understanding their generation. In this work, we analyze over 3 years of continuous wave burst mode data from Van Allen Probes and build a data set of rising and falling tone chorus. For the L shell range covered by Van Allen Probes data (3.5 ≤ L ≤ 7), statistical results demonstrate that the sector where rising tones are most likely to be observed is the dayside during geomagnetically quiet and moderate times and the dawnside during active times. Moreover, rising tone chorus waves have a higher occurrence rate near 5 the equatorial plane, while the falling tone chorus waves have a higher possibility to be observed at lower L-shell and higher magnetic latitude. By analyzing the direction of Poynting wave vector, we statistically investigate the chorus source region size along a field line, and compare the results with previous theoretical estimates. Our analysis confirms previous conclusions that both rising tone and falling tone chorus waves are generated near the equatorial plane, and shows that previous theoretical estimates roughly agree with the observation within a factor of two. Our results provide important insights into further 10 understanding of chorus generation.

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Microburst precipitation of energetic electrons associated with chorus wave generation

Cited by 90 publications

References 14 publications

Effects of cold electron number density variation on whistler-mode wave growth

Effects of cold electron number density variation on whistler-mode wave growth

Spatial spreading of magnetospherically reflected chorus elements in the inner magnetosphere

A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

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