The relationship between the macroscopic state of electrons and the properties of chorus waves observed by the Van Allen Probes

Yue, Chao; An, Xin; Bortnik, J.; Ma, Qianli; Li, Wen; Thorne, R. M.; Reeves, G. D.; Gkioulidou, M.; Mitchell, D. G.; Kletzing, C.

doi:10.1002/2016gl070084

Cited by 53 publications

(67 citation statements)

References 30 publications

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“…This corresponds to the location of a population of >50-mV/m waves identified in Tyler et al (2019), which were associated with plasmasphere erosion during active times. However, both upper-and lower-band chorus have been observed to have oblique populations Yue et al, 2016). The location of these very large-amplitude oblique waves is similar to that of quasi-oblique lower-band chorus observed by Li et al (2016) using time-averaged EMFISIS data.…”

Section: Discussionsupporting

confidence: 67%

Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes

et al. 2019

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We present a statistical analysis with 100% duty cycle and non‐time‐averaged amplitudes of the prevalence and distribution of high‐amplitude >50‐pT whistler mode waves in the outer radiation belt using 5 years of Van Allen Probes data. Whistler mode waves with high magnetic field amplitudes are most common above L=4.5 and between magnetic local time of 0–14 where they are present approximately 1–6% of the time. During high geomagnetic activity, high‐amplitude whistler mode wave occurrence rises above 25% in some regions. The dayside population are more common during quiet or moderate geomagnetic activity and occur primarily >5° from the magnetic equator, while the night‐to‐dawn population are enhanced during active times and are primarily within 5° of the magnetic equator. These results are different from the distribution of electric field peaks discussed in our previous paper covering the same time period and spatial range. Our previous study found large‐amplitude electric field peaks were common down to L=3.5 and were largely absent from afternoon and near noon. The different distribution of large electric and magnetic field amplitudes implies that the low‐L component of whistler mode waves observed previously are primarily highly oblique, while the dayside and high‐L populations are primarily field aligned. These results have important implications for modeling radiation belt particle interactions with chorus, as large‐amplitude waves interact nonlinearly with electrons, resulting in rapid energization, de‐energization, or pitch angle scattering. This also may provide clues regarding the mechanisms which can cause significant whistler mode wave growth up to more than 100 times the average wave amplitude.

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Section: Discussionsupporting

confidence: 67%

Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes

et al. 2019

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“…Spasojevic (2014) also showed a storm intensity dependence on chorus amplitude and occurrence, as larger storms had more, stronger, and longer lasting chorus activity than moderate storms. MacDonald et al (2008MacDonald et al ( , 2010 and Yue et al (2016) have previously shown that when an electron distribution correlated with chorus wave activity is observed, it typically has already relaxed to a more stable state. This was attributed to the changing geomagnetic field configuration with the increased geomagnetic activity of the main phase.…”

Section: Discussionmentioning

confidence: 99%

The Storm Time Development of Source Electrons and Chorus Wave Activity During CME‐ and CIR‐Driven Storms

et al. 2019

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Whistler mode chorus waves influence the dynamics of the Earth's radiation belts and the inner magnetosphere through gyroresonant wave particle interactions. Chorus waves are generated by anisotropic hot electrons from a few to tens of keV, called source electrons, which have increased access from the nightside plasma sheet to the inner magnetosphere during geomagnetic storms. The primary drivers of geomagnetic storms are coronal mass ejections (CMEs) and corotating interaction regions (CIRs). Through differences in their characteristic physical parameters, they can each impact the nightside plasma sheet differently. Using Van Allen Probes observations, we have conducted a superposed epoch analysis of chorus wave activity and source electron development across all local times between L = 2–6 during 25 CME‐ and 35 CIR‐driven storms. The superposed epoch analysis shows that chorus wave power follows the storm phase‐dependent access of the source electron population. Chorus waves and source electrons are observed on the dawnside during the main phase, when open drift path access via eastward convective drift from the plasma sheet is enhanced. During the recovery phase, chorus waves and source electrons are observed at all magnetic local times with low intensities, exemplifying the formation of a weak symmetric, trapped electron population. A linear theory approximation for wave growth from source electron observations shows that increased wave growth follows the enhanced source electrons during each storm phase. CME and CIR storms display similar behavior and levels of average wave power; however, chorus wave activity reaches lower L‐shells during CME storms on average.

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“…Previous studies based on linear theory [Gary and Wang, 1996], PIC simulation , or observation [Gary et al, 2005;Yue et al, 2016] have suggested that the saturation A-‖ relation for whistler mode waves should satisfy equation (1). As discussed in section 1, linear theory cannot determine the value of S or in equation (1), because the distribution is assumed to be the unperturbed initial distribution all the time.…”

Section: The A-‖ Relationshipmentioning

confidence: 99%

“…However, in linear analysis, an assumption about the maximum linear growth rate ( m ) is needed to obtain values for S and . Recently, Yue et al [2016] used Van Allen Probes data and demonstrated that the electron temperature anisotropy constraint associated with excitation of whistler mode chorus waves is well described by equation (1). Here Ω is the unsigned electron cyclotron frequency.…”

Section: Introductionmentioning

confidence: 99%

Quasilinear analysis of saturation properties of broadband whistler mode waves

Tao

Chen

Liu

et al. 2017

Geophysical Research Letters

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Saturation properties of parallel propagating broadband whistler mode waves are investigated using quasilinear theory. By assuming that the electron distribution stays bi‐Maxwellian, we combine the previously obtained energy equation of quasilinear theory with wave equation to self‐consistently model the excitation of broadband whistler waves. The resulting evolution profile of wave intensity, spectrum, and electron temperature are consistent with those from particle‐in‐cell (PIC) simulations. We obtain the inverse relation between the saturation temperature anisotropy (A) and parallel plasma beta (β∥) directly from quasilinear theory. Our A‐β∥ relation agrees very well with previous results from observation and PIC simulation. We also demonstrate that it might be possible to predict the wave amplitude from the initial maximum linear growth rate alone and show that the peak frequency and spectrum width are well‐defined functions of the final β∥ at saturation, but not of the initial β∥.

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The relationship between the macroscopic state of electrons and the properties of chorus waves observed by the Van Allen Probes

Cited by 53 publications

References 30 publications

Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes

Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes

The Storm Time Development of Source Electrons and Chorus Wave Activity During CME‐ and CIR‐Driven Storms

Quasilinear analysis of saturation properties of broadband whistler mode waves

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