Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts

Mann, I. R.; Lee, Eunah; Claudepierre, S. G.; Fennell, J. F.; Degeling, A. W.; Rae, I. J.; Baker, D. N.; Reeves, G. D.; Spence, H. E.; Ozeke, L. G.; Rankin, R.; Milling, D. K.; Kale, A.; Friedel, R.; Honary, F.

doi:10.1038/ncomms3795

Cited by 110 publications

(128 citation statements)

References 28 publications

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“…An equivalent view is that electrons accelerated by E φ move radially inward while conserving their first invariant (Li et al, 1993) tric field pulse will transport only a fraction of the electrons located on the dayside of the magnetosphere, which will lead to drift echoes observed by the Van Allen Probes. Multi-MeV electrons which traverse duskward and stay in drift resonance with azimuthally propagating E φ < 0 are most strongly accelerated (Li et al, 1993;Elkington et al, 2002;Kress et al, 2007;Mann et al, 2013) Figure 6a shows E φ at the time of shock arrival 20:22:00, while Fig. 6b shows E φ at 20:23:00 UT, after the magnetosonic impulse produced by the dayside compression has propagated toward the nightside.…”

Section: October 2013mentioning

confidence: 99%

Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013

et al. 2015

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Abstract. Coronal mass ejection (CME)-shock compression of the dayside magnetopause has been observed to cause both prompt enhancement of radiation belt electron flux due to inward radial transport of electrons conserving their first adiabatic invariant and prompt losses which at times entirely eliminate the outer zone. Recent numerical studies suggest that enhanced ultra-low frequency (ULF) wave activity is necessary to explain electron losses deeper inside the magnetosphere than magnetopause incursion following CME-shock arrival. A combination of radial transport and magnetopause shadowing can account for losses observed at radial distances into L = 4.5, well within the computed magnetopause location. We compare ULF wave power from the Electric Field and Waves (EFW) electric field instrument on the Van Allen Probes for the 8 October 2013 storm with ULF wave power simulated using the Lyon-FedderMobarry (LFM) global magnetohydrodynamic (MHD) magnetospheric simulation code coupled to the Rice Convection Model (RCM). Two other storms with strong magnetopause compression, 8-9 October 2012 and 17-18 March 2013, are also examined. We show that the global MHD model captures the azimuthal magnetosonic impulse propagation speed and amplitude observed by the Van Allen Probes which is responsible for prompt acceleration at MeV energies reported for the 8 October 2013 storm. The simulation also captures the ULF wave power in the azimuthal component of the electric field, responsible for acceleration and radial transport of electrons, at frequencies comparable to the electron drift period. This electric field impulse has been shown to explain observations in related studies (Foster et al., 2015) of electron acceleration and drift phase bunching by the Energetic Particle, Composition, and Thermal Plasma Suite (ECT) instrument on the Van Allen Probes.

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Section: October 2013mentioning

confidence: 99%

Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013

et al. 2015

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“…The linear dependence of df A on dW A suggests that the phase shift of particle PSDs across the resonant energy should also be 180°. Such a phase shift is thus treated as a characteristic signature of ULF waveparticle drift resonance (Claudepierre et al 2013;Dai et al 2013;Mann et al 2013).…”

Section: Simultaneous Resonance Of Ulf Waves With Energetic Electronsmentioning

confidence: 99%

“…This signature has been widely used as a diagnostic to identify drift-resonant waveparticle interactions (Mann et al 2013, Claudepierre et al 2013Dai et al 2013;Hao et al 2014). The diagnostic is derived from Eq.…”

Section: Observational Signatures Of Ulf Wave Drift-resonancementioning

confidence: 99%

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

Zong

Rankin

Zhou

2017

Rev. Mod. Plasma Phys.

137

162

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One of the most important issues in space physics is to identify the dominant processes that transfer energy from the solar wind to energetic particle populations in Earth's inner magnetosphere. Ultra-low-frequency (ULF) waves are an important consideration as they propagate electromagnetic energy over vast distances with little dissipation and interact with charged particles via drift resonance and drift-bounce resonance. ULF waves also take part in magnetosphereionosphere coupling and thus play an essential role in regulating energy flow throughout the entire system. This review summarizes recent advances in the characterization of ULF Pc3-5 waves in different regions of the magnetosphere, including ion and electron acceleration associated with these waves.

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“…For instance, ULF oscillations can act to enhance radial diffusion serving as a diffusive mechanism for the energisation of radiation belt electrons and ions . Also the resonant interaction between azimuthally drifting radiation belt electrons and standing Pc 4-5 ULF waves has been analysed both theoretically and numerically (Schulz and Lanzerotti, 1974;Elkington et al, 2003), and there is growing observational evidence that coherent drift resonance interactions between large-amplitude ULF waves and electrons contribute to electron acceleration in the radiation belts (Mann et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The influence of solar wind variability on magnetospheric ULF wave power

Pokhotelov¹,

Rae²,

Murphy

et al. 2015

Ann. Geophys.

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Abstract. Magnetospheric ultra-low frequency (ULF) oscillations in the Pc 4-5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF) orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind-IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)) of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature), plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind-magnetosphere coupling.

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Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts

Cited by 110 publications

References 28 publications

Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013

Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013

The interaction of ultra-low-frequency pc3-5 waves with charged particles in Earth’s magnetosphere

The influence of solar wind variability on magnetospheric ULF wave power

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