Bibliography

Energetic Electron Precipitation Observed by FIREBIRD-II Potentially Driven by EMIC Waves: Location, Extent, and Energy Range from a Multi-Event Analysis

Abstract We evaluate the location, extent and energy range of electron precipitation driven by ElectroMagnetic Ion Cyclotron (EMIC) waves using coordinated multi-satellite observations from near-equatorial and Low-Earth-Orbit (LEO) missions. Electron precipitation was analyzed using the Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics (FIREBIRD-II) CubeSats, in conjunction either with typical EMIC-driven precipitation signatures observed by Polar Orbiting Environmental Satellites (POES) or with in situ EMIC wave observations from Van Allen Probes. The multi-event analysis shows that electron precipitation occurred in a broad region near dusk (16–23 MLT), mostly confined to 3.5–7.5 L- shells. Each precipitation event occurred on localized radial scales, on average ∼0.3 L. Most importantly, FIREBIRD-II recorded electron precipitation from ∼200–300 keV to the expected ∼MeV energies for most cases, suggesting that EMIC waves can efficiently scatter a wide energy range of electrons.

Capannolo, L.; Li, W.; Spence, H.; Johnson, A.; Shumko, M.; Sample, J.; Klumpar, D.;

Published by: Geophysical Research Letters      Published on: 02/2021

YEAR: 2021     DOI: https://doi.org/10.1029/2020GL091564

electron precipitation; EMIC waves; inner magnetosphere; electron losses; proton precipitation; wave-particle interactions; Van Allen Probes

Diffusive scattering of electrons by electron holes around injection fronts

Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce-averaged diffusion coefficients and demonstrate their dependence on the EH spatial distribution (latitudinal extent and spatial filling factor) and individual EH parameters (amplitude of electrostatic potential, velocity, and spatial scales). We show that EHs can drive pitch angle scattering of math formula5 keV electrons at rates 10-2-10-4 s-1 and, hence, can contribute to electron losses and conjugated diffuse aurora brightenings. The momentum and pitch angle scattering rates can be comparable, so that EHs can also provide efficient electron heating. The scattering rates driven by EHs at L shells L \~ 5\textendash8 are comparable to those due to chorus waves and may exceed those due to electron cyclotron harmonics.

Vasko, I; Agapitov, O.; Mozer, F.; Artemyev, A.; Krasnoselskikh, V.; Bonnell, J.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 03/2017

YEAR: 2017     DOI: 10.1002/2016JA023337

electron holes; electron losses; injection; Radiation belt; solitary waves; Van Allen Probes

Reproducing the observed energy-dependent structure of Earth s electron radiation belts during storm recovery with an event-specific diffusion model

We present dynamic simulations of energy-dependent losses in the radiation belt " slot region" and the formation of the two-belt structure for the quiet days after the March 1st storm. The simulations combine radial diffusion with a realistic scattering model, based data-driven spatially and temporally-resolved whistler mode hiss wave observations from the Van Allen Probes satellites. The simulations reproduce Van Allen Probes observations for all energies and L-shells (2 to 6) including (a) the strong energy-dependence to the radiation belt dynamics (b) an energy-dependent outer boundary to the inner zone that extends to higher L-shells at lower energies and (c) an " S-shaped" energy-dependent inner boundary to the outer zone that results from the competition between diffusive radial transport and losses. We find that the characteristic energy-dependent structure of the radiation belts and slot region is dynamic and can be formed gradually in ~15 days, although the " S-shape" can also be reproduced by assuming equilibrium conditions. The highest energy electrons (E > 300 keV) of the inner region of the outer belt (L ~ 4-5) also constantly decay, demonstrating that hiss wave scattering affects the outer belt during times of extended plasmasphere. Through these simulations, we explain the full structure in energy and L-shell of the belts and the slot formation by hiss scattering during storm recovery. We show the power and complexity of looking dynamically at the effects over all energies and L-shells and the need for using data-driven and event-specific conditions.

Ripoll, J.; Reeves, G.; Cunningham, G.; Loridan, V.; Denton, M.; ik, O.; Kurth, W.; Kletzing, C.; Turner, D.; Henderson, M.; Ukhorskiy, A;

Published by: Geophysical Research Letters      Published on: 05/2016

YEAR: 2016     DOI: 10.1002/2016GL068869

electron lifetimes; electron losses; hiss waves; Radiation belts; Slot region; Van Allen Probes; wave particle interactions

Electron losses from the radiation belts caused by EMIC waves

Electromagnetic Ion Cyclotron (EMIC) waves cause electron loss in the radiation belts by resonating with high-energy electrons at energies greater than about 500 keV. However, their effectiveness has not been fully quantified. Here we determine the effectiveness of EMIC waves by using wave data from the fluxgate magnetometer on CRRES to calculate bounce-averaged pitch angle and energy diffusion rates for L*=3.5\textendash7 for five levels of Kp between 12 and 18 MLT. To determine the electron loss, EMIC diffusion rates were included in the British Antarctic Survey Radiation Belt Model together with whistler mode chorus, plasmaspheric hiss, and radial diffusion. By simulating a 100 day period in 1990, we show that EMIC waves caused a significant reduction in the electron flux for energies greater than 2 MeV but only for pitch angles lower than about 60\textdegree. The simulations show that the distribution of electrons left behind in space looks like a pancake distribution. Since EMIC waves cannot remove electrons at all pitch angles even at 30 MeV, our results suggest that EMIC waves are unlikely to set an upper limit on the energy of the flux of radiation belt electrons.

Kersten, Tobias; Horne, Richard; Glauert, Sarah; Meredith, Nigel; Fraser, Brian; Grew, Russell;

Published by: Journal of Geophysical Research: Space Physics      Published on: 11/2014

YEAR: 2014     DOI: 10.1002/2014JA020366

electron losses; EMIC waves

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus-driven losses

The population of electrons in the Earth\textquoterights outer radiation belt increases when the magnetosphere is exposed to high-speed streams of solar wind, coronal mass ejections, magnetic clouds, or other disturbances. After this increase, the number of electrons decays back to approximately the initial population. This study statistically analyzes the lifetimes of the electron at Geostationary Earth Orbit (GEO) from Los Alamos National Laboratory electron flux data. The decay rate of the electron fluxes are calculated for 14 energies ranging from 24 keV to 3.5 MeV to identify a relationship between the lifetime and energy of the electrons. The statistical data show that electron lifetimes increase with energy. Also, the statistical results show a good agreement up to \~1 MeV with an analytical model of lifetimes, where electron losses are caused by their resonant interaction with oblique chorus waves, using average wave intensities obtained from Cluster statistics. However, above 500 keV, the measured lifetimes increase with energy becomes less steep, almost stopping. This could partly stem from the difficultly of identifying lifetimes larger than 10 days, for high energy, with the methods and instruments of the present study at GEO. It could also result from the departure of the actual geomagnetic field from a dipolar shape, since a compressed field on the dayside should preferentially increase chorus-induced losses at high energies. However, during nearly quiet geomagnetic conditions corresponding to lifetime measurement periods, it is more probably an indication that outward radial diffusion imposes some kind of upper limit on lifetimes of high-energy electrons near geostationary orbit.

Boynton, R.; Balikhin, M.; Mourenas, D.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 08/2014

YEAR: 2014     DOI: 10.1002/2014JA019920

Chorus; electron lifetimes; electron losses; oblique waves