Slow electron phase space holes: Magnetotail observations

Norgren, Cecilia; André, Mats; Vaivads, A.; Khotyaintsev, Yuri V.

doi:10.1002/2015gl063218

Cited by 52 publications

(64 citation statements)

References 25 publications

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“…We have used multispacecraft interferometry to estimate the EH velocities and direction of propagation. Previous multispacecraft interferometry analyses have been restricted to two spacecraft and required assumptions on the direction of EH propagation (Norgren et al, ; Pickett et al, ). Using the multispacecraft interferometry we have found that the EHs propagate quasi‐parallel to the magnetic field with velocities of a few thousands of kilometers per second and have parallel spatial scales of a few Debye lengths.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous Multispacecraft Probing of Electron Phase Space Holes

Tong

Vasko

Mozer

et al. 2018

Geophysical Research Letters

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We present a series of electron holes observed simultaneously on four Magnetospheric Multiscale spacecraft in the plasma sheet boundary layer. The multispacecraft probing shows that the electron holes propagated quasi‐parallel to the local magnetic field with velocities of a few thousand kilometers per second with parallel spatial scales of a few kilometers (a few Debye lengths). The simultaneous multispacecraft probing allows analyzing the 3‐D configuration of the electron holes. We estimate the electric field gradients and charge densities associated with the electrons holes. The electric fields are fit to simple 3‐D electron hole models to estimate their perpendicular scales and demonstrate that the electron holes were generally not axially symmetric with respect to the local magnetic field. We emphasize that most of the electron holes had a complicated structure not reproduced by the simple models widely used in single‐spacecraft studies.

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Section: Discussionmentioning

confidence: 99%

Simultaneous Multispacecraft Probing of Electron Phase Space Holes

Tong

Vasko

Mozer

et al. 2018

Geophysical Research Letters

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“…The generation mechanism of such EHs is likely an electron beam instability [ Morse and Nielson , ; Omura et al , ; Goldman et al , ]. Norgren et al [] and Graham et al [] have also reported observations of much slower EHs likely generated by the Buneman instability.…”

Section: Discussionmentioning

confidence: 99%

Electron holes in the outer radiation belt: Characteristics and their role in electron energization

et al. 2017

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Van Allen Probes have detected electron holes (EHs) around injection fronts in the outer radiation belt. Presumably generated near equator, EHs propagate to higher latitudes potentially resulting in energization of electrons trapped within EHs. This process has been recently shown to provide electrons with energies up to several tens of keV and requires EH propagation up to rather high latitudes. We have analyzed more than 100 EHs observed around a particular injection to determine their kinetic structure and potential energy sources supporting the energization of trapped electrons. EHs propagate with velocities from 1000 to 20,000 km/s (a few times larger than the thermal velocity of the coldest background electron population). The parallel scale of observed EHs is from 0.3 to 3 km that is of the order of hundred Debye lengths. The perpendicular to parallel scale ratio is larger than one in a qualitative agreement with the theoretical scaling relation. The amplitudes of EH electrostatic potentials are generally below 100 V. We determine the properties of the electron population trapped within EHs by making use of the Bernstein‐Green‐Kruskal analysis and via analysis of EH magnetic field signatures. The density of the trapped electron population is on average 20% of the background electron density. The perpendicular temperature of the trapped population is on average 300 eV and is larger for faster EHs. We show that energy losses of untrapped electrons scattered by EHs in the inhomogeneous background magnetic field may balance the energization of trapped electrons.

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“…The primary axis

false(\overset{z}{true} false)

is chosen parallel to B 0 . This particular model has the advantages of straightforward integration and distinct parallel and perpendicular length scales and has been successfully applied to both theory and observations in several instances (Andersson et al, ; Chen et al, , ; Norgren et al, ; Tao et al, ), so those results can be compared easily.

normalΦ false(r, z false) = Φ_{0} e^{- \frac{r^{2}}{2 L_{⊥}^{2}}} e^{- \frac{z^{2}}{2 L_{∥}^{2}}}

…”

Section: Analytic Modelmentioning

confidence: 99%

Electron Phase‐Space Holes in Three Dimensions: Multispacecraft Observations by Magnetospheric Multiscale

et al. 2018

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Electron phase‐space holes are kinetic plasma structures commonly observed in space plasmas on Debye length scales. Near the Earth's duskside flank at 10 Earth radii, a series of 32 electron holes (EHs) are detected within a 1‐s window on all four Magnetospheric Multiscale spacecraft. The spacecraft separation of <7 km is similar to the expected EH size in this region. Length, width, amplitude, and relative positions are determined for individual EHs using a cylindrically symmetric model fit to Magnetospheric Multiscale E field measurements. The model shows good agreement with observed E fields far from the EH center. Deviations in E⊥ from the model are present near the center, indicating observed EHs have complex, sometimes irregular, internal structure. Perturbation magnetic fields δB modeled assuming an E × B0 electron current reproduce the measured parallel perturbation in most cases, although there is a systematic variation due to geometric and finite gyroradius effects. Many EHs in this event have large amplitude for their size, reaching the theoretical lower limit in length parallel to the background magnetic field, which requires the electron phase‐space density to approach 0 in the center. It is possible that EHs of this type have recently formed, eventually weakening or becoming longer over time. This study provides the most detailed measurements of EHs to date. Their derived properties are largely in agreement with expectations from previous research. It remains unclear whether the few notable differences are due to rapid time evolution or are specific to the local environment.

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Slow electron phase space holes: Magnetotail observations

Cited by 52 publications

References 25 publications

Simultaneous Multispacecraft Probing of Electron Phase Space Holes

Simultaneous Multispacecraft Probing of Electron Phase Space Holes

Electron holes in the outer radiation belt: Characteristics and their role in electron energization

Electron Phase‐Space Holes in Three Dimensions: Multispacecraft Observations by Magnetospheric Multiscale

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