Bursty Bulk Flow Turbulence as a Source of Energetic Particles to the Outer Radiation Belt

Ergun, Robert E; Usanova, Maria; Turner, D. L.; Stawarz, J. E.

doi:10.1029/2022gl098113

Cited by 11 publications

(11 citation statements)

References 45 publications

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“…They are very similar to other turbulent events discussed in Ergun et al. (2015, 2020, 2022) and Stawarz et al. (2015).…”

Section: Observationssupporting

confidence: 90%

“…The black circles represent the measured PSDs, the blue lines refer to the inertial region, the orange and green lines are power-law fits. They are very similar to other turbulent events discussed in Ergun et al (2015Ergun et al ( , 2020Ergun et al ( , 2022 and Stawarz et al (2015). The spectral index in the inertial region is consistent with −5/3 for B and −1.25 for E, which is often seen in the BBF braking region.…”

Section: Observationssupporting

confidence: 85%

“…For example, these fields can be associated with inner magnetospheric plasma wave modes like time-domain structures (TDS; e.g., Mozer et al, 2013Mozer et al, , 2015. In this work, in support of the results by Ergun et al (2022), we focus on the BBF breaking region (Re = 5-15) and turbulent energization within it; we leave the investigation of energization processes in the inner magnetosphere to a follow-up study. As we concentrate on electron energization in flow bursts, we set additional criteria to select flow burst events: magnetic field fluctuations, |dB| (defined as B, detrended in a 100-s moving window), must exceed 5 nT and the maximum ion speed within a ±30 s interval around the identified electric field peak must be greater than the speed threshold.…”

Section: Automated Event Detection Algorithm and Bbf Selection Criteriamentioning

confidence: 69%

“…A companion paper by Ergun et al. (2022) presents theory and test‐particle simulations. In Section 2, we describe THEMIS orbits and instrumentation used for this study.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we expand on the Ergun et al (2015) study and investigate the relationship between the observed turbulent electric fields and electron energization in flow bursts statistically. A companion paper by Ergun et al (2022) presents theory and test-particle simulations. In Section 2, we describe THEMIS orbits and instrumentation used for this study.…”

mentioning

confidence: 99%

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Electron Energization by High‐Amplitude Turbulent Electric Fields: A Possible Source of the Outer Radiation Belt

Usanova

Ergun

2022

JGR Space Physics

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Bursty bulk flows (BBFs) are high-speed plasma flow events, observed in Earth's magnetotail (Angelopoulos et al., 1992;Baumjohann et al., 1990). They are believed to be generated by magnetic reconnection in the tail at distances greater than about ∼20-30 Earth radii (Re) (Chen & Wolf, 1993). Earthward BBFs observed in the plasma sheet within a wide range of geocentric distances from 5 to 30 Re are characterized by dipolarization (an increase in the B z magnetic field component) and a decrease in plasma density and plasma pressure (Ohtani et al., 2004). BBFs are spatially localized in the direction of the flow and are often confined to <3 Re in the dawn-dusk direction (Angelopoulos et al., 1997). Due to their localization, these events are most often observed as bursts ∼10 min duration. Between 10 and 20 Re their speeds reach several hundred to over a thousand km/s in earthward direction. As BBFs move closer to Earth (6-12 Re tailward), they slow down and deflect as their energy dissipates (Shiokawa et al., 1997). The region over which the flow is slowed and diverted in the near-Earth tail is known as the BBF braking region.The flow braking can generate turbulent plasma fluctuations and instabilities (e.g., El-Alaoui et al., 2013;Shiokawa et al., 2005). These fluctuations can exhibit properties of MHD-and kinetic scale Alfvén waves being involved in a turbulent cascade in BBFs (Chaston et al., 2012(Chaston et al., , 2014Stawarz et al., 2015). The energy cascade has also been found associated with tail reconnection (Dai et al., 2011;Ergun et al., 2020) and observed in the plasma sheet boundary layer between 4 and 6 Re (Wygant et al., 2002). Ergun et al. (2015) found that BBF braking events can be accompanied by high-amplitude electric fields (>50 mV/m). The large-amplitude electric fields have been observed at radial distances between 10 and 13 Re

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“…They are very similar to other turbulent events discussed in Ergun et al. (2015, 2020, 2022) and Stawarz et al. (2015).…”

Section: Observationssupporting

confidence: 90%

Section: Observationssupporting

confidence: 85%

Section: Automated Event Detection Algorithm and Bbf Selection Criteriamentioning

confidence: 69%

“…A companion paper by Ergun et al. (2022) presents theory and test‐particle simulations. In Section 2, we describe THEMIS orbits and instrumentation used for this study.…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Electron Energization by High‐Amplitude Turbulent Electric Fields: A Possible Source of the Outer Radiation Belt

Usanova

Ergun

2022

JGR Space Physics

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Particle Acceleration by Magnetic Reconnection in Geospace

Oka,

Birn,

Egedal

et al. 2023

Space Sci Rev

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Particles are accelerated to very high, non-thermal energies during explosive energy-release phenomena in space, solar, and astrophysical plasma environments. While it has been established that magnetic reconnection plays an important role in the dynamics of Earth’s magnetosphere, it remains unclear how magnetic reconnection can further explain particle acceleration to non-thermal energies. Here we review recent progress in our understanding of particle acceleration by magnetic reconnection in Earth’s magnetosphere. With improved resolutions, recent spacecraft missions have enabled detailed studies of particle acceleration at various structures such as the diffusion region, separatrix, jets, magnetic islands (flux ropes), and dipolarization front. With the guiding-center approximation of particle motion, many studies have discussed the relative importance of the parallel electric field as well as the Fermi and betatron effects. However, in order to fully understand the particle acceleration mechanism and further compare with particle acceleration in solar and astrophysical plasma environments, there is a need for further investigation of, for example, energy partition and the precise role of turbulence.

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The Interplay Between Collisionless Magnetic Reconnection and Turbulence

Stawarz,

Muñoz,

Bessho

et al. 2024

Space Sci Rev

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Alongside magnetic reconnection, turbulence is another fundamental nonlinear plasma phenomenon that plays a key role in energy transport and conversion in space and astrophysical plasmas. From a numerical, theoretical, and observational point of view there is a long history of exploring the interplay between these two phenomena in space plasma environments; however, recent high-resolution, multi-spacecraft observations have ushered in a new era of understanding this complex topic. The interplay between reconnection and turbulence is both complex and multifaceted, and can be viewed through a number of different interrelated lenses - including turbulence acting to generate current sheets that undergo magnetic reconnection (turbulence-driven reconnection), magnetic reconnection driving turbulent dynamics in an environment (reconnection-driven turbulence) or acting as an intermediate step in the excitation of turbulence, and the random diffusive/dispersive nature of the magnetic field lines embedded in turbulent fluctuations enabling so-called stochastic reconnection. In this paper, we review the current state of knowledge on these different facets of the interplay between turbulence and reconnection in the context of collisionless plasmas, such as those found in many near-Earth astrophysical environments, from a theoretical, numerical, and observational perspective. Particular focus is given to several key regions in Earth’s magnetosphere – namely, Earth’s magnetosheath, magnetotail, and Kelvin-Helmholtz vortices on the magnetopause flanks – where NASA’s Magnetospheric Multiscale mission has been providing new insights into the topic.

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Bursty Bulk Flow Turbulence as a Source of Energetic Particles to the Outer Radiation Belt

Cited by 11 publications

References 45 publications

Electron Energization by High‐Amplitude Turbulent Electric Fields: A Possible Source of the Outer Radiation Belt

Electron Energization by High‐Amplitude Turbulent Electric Fields: A Possible Source of the Outer Radiation Belt

Particle Acceleration by Magnetic Reconnection in Geospace

The Interplay Between Collisionless Magnetic Reconnection and Turbulence

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