Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation

In August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic (<200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through the high density region during multiple orbits, showing that the structure was spatial and relatively stable over many hours. The region, identified as a plasmaspheric plume, was filled with intense hiss-like plasma waves. We use a quasi-linear diffusion model to investigate plume whistler-mode hiss waves as the cause of precipitation observed by BARREL. The model input parameters are based on the observed wave, plasma and energetic particle properties obtained from Van Allen Probes. Diffusion coefficients are found to be largest in the same energy range as the precipitation observed by BARREL, indicating that the plume hiss waves were responsible for the precipitation. The event-driven pitch angle diffusion simulation is also used to investigate the evolution of the electron phase space density (PSD) for different energies and assumed initial pitch angle distributions. The results show a complex temporal evolution of the phase space density, with periods of both growth and loss. The earliest dynamics, within the ∼5 first minutes, can be controlled by a growth of the PSD near the loss cone (by a factor up to ∼2, depending on the conditions, pitch angle, and energy), favored by the absence of a gradient at the loss cone and by the gradients of the initial pitch angle distribution. Global loss by 1-3 orders of magnitude (depending on the energy) occurs within the first ∼100 min of wave-particle interaction. The prevalence of plasmaspheric plumes and detached plasma regions suggests whistler-mode hiss waves could be an important driver of electron loss even at high L-value (L ∼6), outside of the main plasmasphere.

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Substorm Injections as a Source of Relativistic Electrons in Earth’s Outer Radiation Belt

10.5194/egusphere-egu2020-5801 ◽

2020 ◽

Author(s):

Drew Turner ◽

Ian Cohen ◽

Kareem Sorathia ◽

Sasha Ukhorskiy ◽

Geoff Reeves ◽

...

Keyword(s):

Phase Space ◽

Plasma Sheet ◽

Radiation Belt ◽

Energetic Electron ◽

Local Source ◽

Relativistic Electrons ◽

Phase Space Density ◽

Outer Radiation Belt ◽

Space Density ◽

Van Allen Probes

<p>Earth&#8217;s magnetotail plasma sheet plays a crucial role in the variability of Earth&#8217;s outer electron radiation belt. Typically, injections of energetic electrons from Earth&#8217;s magnetotail into the outer radiation belt and inner magnetosphere during periods of substorm activity are not observed exceeding ~300 keV. &#160;Consistent with that, phase space density radial distributions of electrons typically indicate that for electrons below ~300 keV, there is a source of electrons in the plasma sheet while for electrons with energies above that, there is a local source within the outer radiation belt itself.&#160; However, here we ask the question: is this always the case or can the plasma sheet provide a direct source of relativistic (> ~500 keV) electrons into Earth&#8217;s outer radiation belt via substorm injection? Using phase space density analysis for fixed values of electron first and second adiabatic invariants, we use energetic electron data from NASA&#8217;s Van Allen Probes and Magnetospheric Multiscale (MMS) missions during periods in which MMS observed energetic electron injections in the plasma sheet while Van Allen Probes concurrently observed injections into the outer radiation belt. We report on cases that indicate there was a sufficient source of up to >1 MeV electrons in the electron injections in the plasma sheet as observed by MMS, yet Van Allen Probes did not see those energies injected inside of geosynchronous orbit.&#160; From global insight with recent test-particle simulations in global, dynamic magnetospheric fields, we offer an explanation for why the highest-energy electrons might not be able to inject into the outer belt even while the lower energy (< ~300 keV) electrons do. Two other intriguing points that we will discuss concerning these results are: i) what acceleration mechanism is capable of producing such abundance of relativistic electrons at such large radial distances (X-GSE < -10 RE) in Earth&#8217;s magnetotail? and ii) during what conditions (if any) might injections of relativistic electrons be able to penetrate into the outer belt?</p>

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Phase Space Density matching of relativistic electrons using the Van Allen Probes: REPT results

Geophysical Research Letters ◽

10.1002/grl.50909 ◽

2013 ◽

Vol 40 (18) ◽

pp. 4798-4802 ◽

Cited By ~ 19

Author(s):

S. K. Morley ◽

M. G. Henderson ◽

G. D. Reeves ◽

R. H. W. Friedel ◽

D. N. Baker

Keyword(s):

Phase Space ◽

Relativistic Electrons ◽

Phase Space Density ◽

Space Density ◽

Van Allen Probes

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The generation of Ganymede's diffuse aurora through pitch angle scattering

Annales Geophysicae ◽

10.5194/angeo-35-239-2017 ◽

2017 ◽

Vol 35 (2) ◽

pp. 239-252

Author(s):

Arvind K. Tripathi ◽

Rajendra P. Singhal ◽

Onkar N. Singh II

Keyword(s):

Electron Temperature ◽

Pitch Angle ◽

Atomic Oxygen ◽

Particle Interaction ◽

Distribution Functions ◽

Dissociative Excitation ◽

Kappa Distribution ◽

Loss Cone ◽

Whistler Mode ◽

Whistler Mode Waves

Abstract. Diffuse auroral intensities of neutral atomic oxygen OI λ1356 Å emission on Ganymede due to whistler mode waves are estimated. Pitch angle diffusion of magnetospheric electrons into the loss cone due to resonant wave–particle interaction of whistler mode waves is considered, and the resulting electron precipitation flux is calculated. The analytical yield spectrum approach is used for determining the energy deposition of electrons precipitating into the atmosphere of Ganymede. It is found that the intensities (4–30 R) calculated from the precipitation of magnetospheric electrons observed near Ganymede are inadequate to account for the observational intensities (≤ 100 R). This is in agreement with the conclusions reached in previous works. Some acceleration mechanism is required to energize the magnetospheric electrons. In the present work we consider the heating and acceleration of magnetospheric electrons by electrostatic waves. Two particle distribution functions (Maxwellian and kappa distribution) are used to simulate heating and acceleration of electrons. Precipitation of a Maxwellian distribution of electrons can produce about 70 R intensities of OI λ1356 Å emission for electron temperature of 150 eV. A kappa distribution can also yield a diffuse auroral intensity of similar magnitude for a characteristic energy of about 100 eV. The maximum contribution to the estimated intensity results from the dissociative excitation of O2. Contributions from the direct excitation of atomic oxygen and cascading in atomic oxygen are estimated to be only about 1 and 2 % of the total calculated intensity, respectively. The findings of this work are relevant for the present JUNO and future JUICE missions to Jupiter. These missions will provide new data on electron densities, electron temperature and whistler mode wave amplitudes in the magnetosphere of Jupiter near Ganymede.

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Similarity of Jupiter and RRATs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311006624 ◽

2010 ◽

Vol 6 (S274) ◽

pp. 85-88

Author(s):

Ilknur Gezer ◽

E. Rennan Pekünlü

Keyword(s):

Phase Space ◽

Synchrotron Radiation ◽

Particle Interaction ◽

Plasma Waves ◽

Phase Space Density ◽

Space Density ◽

Wave Particle Interaction ◽

Radio Transients ◽

Rotating Radio Transients ◽

Pioneer 10

AbstractIn the present investigation, radial diffusion of equatorially trapped electrons in the magnetospheres of Jupiter and Rotating Radio Transients (RRATs) are examined and compared. It is assumed that electrons lose energy through synchrotron radiation and the wave-particle interaction. The phase space density of the electrons, which go through gradB drift in Jupiter's and RRATs magnetospheres and thus resonate with the plasma waves, changes and this change predicted by the model seems to be consistent with the Pioneer 10 and Pioneer 11 data for Jupiter's case and a similar result obtained for RRATs.

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Modeling gradual diffusion changes in radiation belt electron phase space density for the March 2013 Van Allen Probes case study

Journal of Geophysical Research Space Physics ◽

10.1002/2014ja020359 ◽

2014 ◽

Vol 119 (10) ◽

pp. 8396-8403 ◽

Cited By ~ 14

Author(s):

Zhao Li ◽

Mary Hudson ◽

Allison Jaynes ◽

Alexander Boyd ◽

David Malaspina ◽

...

Keyword(s):

Phase Space ◽

Radiation Belt ◽

Phase Space Density ◽

Space Density ◽

Van Allen Probes

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Interaction of ULF waves with different ion species: Pitch angle and phase space density implications

Journal of Geophysical Research Space Physics ◽

10.1002/2016ja022995 ◽

2016 ◽

Vol 121 (10) ◽

pp. 9459-9472 ◽

Cited By ~ 17

Author(s):

Jie Ren ◽

Q. G. Zong ◽

X. Z. Zhou ◽

R. Rankin ◽

Y. F. Wang

Keyword(s):

Phase Space ◽

Pitch Angle ◽

Ulf Waves ◽

Phase Space Density ◽

Space Density ◽

Ion Species

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Gradual diffusion and punctuated phase space density enhancements of highly relativistic electrons: Van Allen Probes observations

Geophysical Research Letters ◽

10.1002/2013gl058942 ◽

2014 ◽

Vol 41 (5) ◽

pp. 1351-1358 ◽

Cited By ~ 89

Author(s):

D. N. Baker ◽

A. N. Jaynes ◽

X. Li ◽

M. G. Henderson ◽

S. G. Kanekal ◽

...

Keyword(s):

Phase Space ◽

Relativistic Electrons ◽

Phase Space Density ◽

Space Density ◽

Van Allen Probes

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Statistical Study of Pitch Angle Diffusion during Substorm Injections

10.5194/egusphere-egu2020-12266 ◽

2020 ◽

Author(s):

Reihaneh Ghaffari ◽

Christopher Cully

Keyword(s):

Pitch Angle ◽

Energetic Electron ◽

Loss Cone ◽

Linear Diffusion ◽

Whistler Mode ◽

Wave Measurements ◽

Whistler Mode Waves ◽

Substorm Injection ◽

Injection Region

<p>Energetic Electron Precipitation (EEP) associated with substorm injections typically occurs when magnetospheric waves, particularly whistler-mode waves, resonantly interact with electrons to affect their equatorial pitch angle. This can be considered as a diffusion process that scatters particles into the loss cone. In this study, we investigate whistler-mode wave generation in conjunction with electron injections using in-situ wave measurements by the Themis mission. We calculate the pitch angle diffusion coefficient exerted by the observed wave activity using the quasi-linear diffusion approximation and estimate scattering efficiency in the substorm injection region to constrain where and how much scattering happens typically during these events.</p>

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