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

Tyler, E.; Breneman, A. W.; Cattell, C. A.; Wygant, J. R.; Thaller, S. A.; Malaspina, D.

doi:10.1029/2019ja026913

Cited by 15 publications

(14 citation statements)

References 37 publications

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“…This corresponds to the duskside region, near the inner edge of the outer radiation belt, outside the plasmapause. This region is outside of the peak location of chorus observations, which is on the dawn and dayside, particularly at times of low to moderate geomagnetic activity, but well within the region of observed chorus waves (Li et al, 2016;Tyler et al, 2019aTyler et al, , 2019b. Latitudinally, at 0145 UT, the two satellites are at~12°M LAT (RBSP A) and~21°MLAT (Arase).…”

Section: 1029/2020ja028315mentioning

confidence: 66%

First Direct Observations of Propagation of Discrete Chorus Elements From the Equatorial Source to Higher Latitudes, Using the Van Allen Probes and Arase Satellites

et al. 2020

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Whistler mode chorus waves have recently been established as the most likely candidate for scattering relativistic electrons to produce the electron microbursts observed by low altitude satellites and balloons. These waves would have to propagate from the equatorial source region to significantly higher magnetic latitude in order to scatter electrons of these relativistic energies. This theoretically proposed propagation has never been directly observed. We present the first direct observations of the same discrete rising tone chorus elements propagating from a near equatorial (Van Allen Probes) to an off-equatorial (Arase) satellite. The chorus is observed first on the more equatorial satellite and is found to be more oblique and significantly attenuated at the off-equatorial satellite. This is consistent with the prevailing theory of chorus propagation and with the idea that chorus must propagate from the equatorial source region to higher latitudes. Ray tracing of chorus at the observed frequencies confirms that these elements could be generated parallel to the field at the equator, and propagate through the medium unducted to Van Allen Probes A and then to Arase with the observed time delay, and have the observed obliquity and intensity at each satellite.

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Section: 1029/2020ja028315mentioning

confidence: 66%

First Direct Observations of Propagation of Discrete Chorus Elements From the Equatorial Source to Higher Latitudes, Using the Van Allen Probes and Arase Satellites

et al. 2020

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“…Landau resonance due to chorus waves may contribute to the enhancement of low pitch angle electrons at energies below several hundred eV especially when the waves are oblique (e.g., Li et al, 2019;Ma et al, 2017). The highly oblique chorus waves or the quasi-electrostatic whistler mode waves (Li et al, 2016;Tyler et al, 2019) are not included in our statistical survey. The large electric field component of the waves compared to the magnetic field component indicates the effects of Landau resonance (e.g., Agapitov et al, 2018), which potentially leads to the energetic 10.1029/2020GL088798 electron flux enhancement (e.g., Artemyev et al, 2016).…”

Section: Summary and Discussionmentioning

confidence: 99%

Global Survey of Plasma Sheet Electron Precipitation due to Whistler Mode Chorus Waves in Earth's Magnetosphere

Connor

Zhang

et al. 2020

Geophysical Research Letters

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Whistler mode chorus waves can scatter plasma sheet electrons into the loss cone and produce the Earth's diffuse aurora. Van Allen Probes observed plasma sheet electron injections and intense chorus waves on 24 November 2012. We use quasilinear theory to calculate the precipitating electron fluxes, demonstrating that the chorus waves could lead to high differential energy fluxes of precipitating electrons with characteristic energies of 10–30 keV. Using this method, we calculate the precipitating electron flux from 2012 to 2019 when the Van Allen Probes were near the magnetic equator and perform global surveys of electron precipitation under different geomagnetic conditions. The most significant electron precipitation due to chorus is found from the nightside to dawn sectors over 4 < L < 6.5. The average total precipitating energy flux is enhanced during disturbed conditions, with time‐averaged values reaching ~3–10 erg/cm2/s when AE ≥ 500 nT.

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“…Although the universal applicability of quasilinear theory is called into question by the presence of discrete, large‐amplitude chorus (e.g., Cattell et al, 2008; Cully et al, 2008; Kellogg et al, 2011; Tyler et al, 2019; Wilson et al, 2011), test particle simulations have demonstrated its general validity for small amplitude and broadband waves (Tao et al, 2011). Moreover, recent multidimensional diffusion simulations reproduced the main features of observed radiation belt electron dynamics (Albert et al, 2009; Drozdov et al, 2015; Fok et al, 2008; Fok et al, 2014; Glauert et al, 2014; W. Li, Ma, et al, 2016; Ma et al, 2018; Shprits et al, 2009; Thorne et al, 2013a; Tu et al, 2014; Xiao et al, 2014; Zheng et al, 2014).…”

Section: Local Energy and Pitch Angle Scatteringmentioning

confidence: 99%

Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era

2019

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Discovery of the Earth's Van Allen radiation belts by instruments flown on Explorer 1 in 1958 was the first major discovery of the Space Age. The observation of distinct inner and outer zones of trapped megaelectron volt (MeV) particles, primarily protons at low altitude and electrons at high altitude, led to early models for source and loss mechanisms including Cosmic Ray Albedo Neutron Decay for inner zone protons, radial diffusion for outer zone electrons and loss to the atmosphere due to pitch angle scattering. This scattering lowers the mirror altitude for particles in their bounce motion parallel to the Earth's magnetic field until they suffer collisional loss. A view of the belts as quasi‐static inner and outer zones of energetic particles with different sources was modified by observations made during the Solar Cycle 22 maximum in solar activity over 1989–1991. The dynamic variability of outer zone electrons was measured by the Combined Radiation Release and Effects Satellite launched in July 1990. This variability is caused by distinct types of heliospheric structure that vary with the solar cycle. The launch of the twin Van Allen Probes in August 2012 has provided much longer and more comprehensive measurements during the declining phase of Solar Cycle 24. Roughly half of moderate geomagnetic storms, determined by intensity of the ring current carried mostly by protons at hundreds of kiloelectron volts, produce an increase in trapped relativistic electron flux in the outer zone. Mechanisms for accelerating electrons of hundreds of electron volts stored in the tail region of the magnetosphere to MeVenergies in the trapping region are described in this review: prompt and diffusive radial transport and local acceleration driven by magnetospheric waves. Such waves also produce pitch angle scattering loss, as does outward radial transport, enhanced when the magnetosphere is compressed. While quasilinear simulations have been used to successfully reproduce many essential features of the radiation belt particle dynamics, nonlinear wave‐particle interactions are found to be potentially important for causing more rapid particle acceleration or precipitation. The findings on the fundamental physics of the Van Allen radiation belts potentially provide insights into understanding energetic particle dynamics at other magnetized planets in the solar system, exoplanets throughout the universe, and in astrophysical and laboratory plasmas. Computational radiation belt models have improved dramatically, particularly in the Van Allen Probes era, and assimilative forecasting of the state of the radiation belts has become more feasible. Moreover, machine learning techniques have been developed to specify and predict the state of the Van Allen radiation belts. Given the potential Space Weather impact of radiation belt variability on technological systems, these new radiation belt models are expected to play a critical role in our technological society in the future as much as meteorological models do today.

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

Cited by 15 publications

References 37 publications

First Direct Observations of Propagation of Discrete Chorus Elements From the Equatorial Source to Higher Latitudes, Using the Van Allen Probes and Arase Satellites

First Direct Observations of Propagation of Discrete Chorus Elements From the Equatorial Source to Higher Latitudes, Using the Van Allen Probes and Arase Satellites

Global Survey of Plasma Sheet Electron Precipitation due to Whistler Mode Chorus Waves in Earth's Magnetosphere

Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era

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