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Found 21 entries in the Bibliography.
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2020 
MultiParameter Chorus and Plasmaspheric Hiss Wave Models Abstract The resonant interaction of energetic particles with plasma waves, such as chorus and plasmaspheric hiss waves, plays a direct and crucial role in the acceleration and loss of radiation belt electrons that ultimately affect the dynamics of the radiation belts. In this study, we use the comprehensive wave data measurements made by the Electric and Magnetic Field Instrument Suite and Integrated Science instruments on board the two Van Allen probes, to develop multiparameter statistical chorus and plasmaspheric hiss w ... Aryan, Homayon; Bortnik, Jacob; Meredith, Nigel; Horne, Richard; Sibeck, David; Balikhin, Michael; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2020 YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028403 chorus waves; inner magnetosphere; multi parameter wave distribution; plasmaspheric hiss waves; Van Allen Probes; waveparticle interactions 
The Implications of Temporal Variability in WaveParticle Interactions in Earth s Radiation Belts Changes in electron flux in Earth s outer radiation belt can be modeled using a diffusionbased framework. Diffusion coefficients D for such models are often constructed from statistical averages of observed inputs. Here, we use stochastic parameterization to investigate the consequences of temporal variability in D. Variability time scales are constrained using Van Allen Probe observations. Results from stochastic parameterization experiments are compared with experiments using D constructed from averaged inputs and an aver ... Watt, C.; Allison, H.; Thompson, R.; Bentley, S.; Meredith, N.; Glauert, S.; Horne, R.; Rae, I.; Published by: Geophysical Research Letters Published on: 12/2020 YEAR: 2020 DOI: https://doi.org/10.1029/2020GL089962 probabilistic methods; stochastic parameterization; Van Allen Probes 
A New Approach to Constructing Models of Electron Diffusion by EMIC Waves in the Radiation Belts Electromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron losses in the radiation belts through diffusion via resonant waveparticle interactions. We present a new approach for calculating bounce and driftaveraged EMIC electron diffusion coefficients. We calculate bounceaveraged diffusion coefficients, using quasilinear theory, for each individual Combined Release and Radiation Effects Satellite (CRRES) EMIC wave observation using fitted wave properties, the plasma density and the backgrou ... Ross, J.; Glauert, S.; Horne, R.; Watt, C.; Meredith, N.; Woodfield, E.; Published by: Geophysical Research Letters Published on: 10/2020 YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088976 Radiation belts; EMIC waves; electron diffusion; Van Allen Probes 
Global Model of Whistler Mode Chorus in the NearEquatorial Region (λm< 18°) We extend our database of whistler mode chorus, based on data from seven satellites, by including ∼3 years of data from Radiation Belt Storm Probes (RBSP)A and RBSPB and an additional ∼6 years of data from Time History of Events and Macroscale Interactions during Substorms (THEMIS)A, THEMISD, and THEMISE. The new database allows us to probe the nearequatorial region in detail, revealing new features. In the equatorial source region, λm<6°, strong wave power is most extensive in the 0.1–0.4fce bands in the r ... Meredith, Nigel; Horne, Richard; Shen, XiaoChen; Li, Wen; Bortnik, Jacob; Published by: Geophysical Research Letters Published on: 05/2020 YEAR: 2020 DOI: https://doi.org/10.1029/2020GL087311 whistler mode chorus; waveparticle interactions; Radiation belts; Van Allen Probes 
2019 
Variability of Quasilinear Diffusion Coefficients for Plasmaspheric Hiss In the outer radiation belt, the acceleration and loss of highenergy electrons is largely controlled by waveparticle interactions. Quasilinear diffusion coefficients are an efficient way to capture the smallscale physics of waveparticle interactions due to magnetospheric wave modes such as plasmaspheric hiss. The strength of quasilinear diffusion coefficients as a function of energy and pitch angle depends on both wave parameters and plasma parameters such as ambient magnetic field strength, plasma number density, and co ... Watt, C.; Allison, H.; Meredith, N.; Thompson, R.; Bentley, S.; Rae, I.; Glauert, S.; Horne, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2018JA026401 empirical; Magnetosphere; parameterization; stochastic; Van Allen Probes; waveparticle interactions 
2018 
Global model of plasmaspheric hiss from multiple satellite observations We present a global model of plasmaspheric hiss, using data from eight satellites, extending the coverage and improving the statistics of existing models. We use geomagnetic activity dependent templates to separate plasmaspheric hiss from chorus. In the region 2214 MLT the boundary between plasmaspheric hiss and chorus moves to lower L* values with increasing geomagnetic activity. The average wave intensity of plasmaspheric hiss is largest on the dayside and increases with increasing geomagnetic activity from midnight throu ... Meredith, Nigel; Horne, Richard; Kersten, Tobias; Li, Wen; Bortnik, Jacob; SicardPiet, elica; Yearby, Keith; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2018 YEAR: 2018 DOI: 10.1029/2018JA025226 plasmasphere; Plasmaspheric Hiss; Radiation belts; Van Allen Probes 
2014 
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 highenergy 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 bounceaveraged 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 ... 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 
In the Earth\textquoterights radiation belts the flux of relativistic electrons is highly variable, sometimes changing by orders of magnitude within a few hours. Since energetic electrons can damage satellites it is important to understand the processes driving these changes and, ultimately, to develop forecasts of the energetic electron population. One approach is to use threedimensional diffusion models, based on a FokkerPlanck equation. Here we describe a model where the phasespace density is set to zero at the outer L ... Glauert, Sarah; Horne, Richard; Meredith, Nigel; Published by: Journal of Geophysical Research: Space Physics Published on: 09/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.910.1002/2014JA020092 
Threedimensional stochastic modeling of radiation belts in adiabatic invariant coordinates A 3D model for solving the radiation belt diffusion equation in adiabatic invariant coordinates has been developed and tested. The model, named Radbelt Electron Model, obtains a probabilistic solution by solving a set of It\^o stochastic differential equations that are mathematically equivalent to the diffusion equation. This method is capable of solving diffusion equations with a full 3D diffusion tensor, including the radiallocal cross diffusion components. The correct form of the boundary condition at equatorial pitch ... Zheng, Liheng; Chan, Anthony; Albert, Jay; Elkington, Scot; Koller, Josef; Horne, Richard; Glauert, Sarah; Meredith, Nigel; Published by: Journal of Geophysical Research: Space Physics Published on: 09/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.910.1002/2014JA020127 adiabatic invariant coordinates; diffusion equation; fully 3D model; Radiation belt; stochastic differential equation 
2008 
This paper focuses on the modeling of local acceleration and loss processes in the outer radiation belt. We begin by reviewing the statistical properties of waves that violate the first and second adiabatic invariants, leading to the loss and acceleration of high energy electrons in the outer radiation belt. After a brief description of the most commonly accepted methodology for computing quasilinear diffusion coefficients, we present pitchangle scattering simulations by (i) plasmaspheric hiss, (ii) a combination of plasma ... SHPRITS, Y; SUBBOTIN, D; MEREDITH, N; ELKINGTON, S; Published by: Journal of Atmospheric and SolarTerrestrial Physics Published on: 11/2008 YEAR: 2008 DOI: 10.1016/j.jastp.2008.06.014 
In this paper, we focus on the modeling of radial transport in the Earth\textquoterights outer radiation belt. A historical overview of the first observations of the radiation belts is presented, followed by a brief description of radial diffusion. We describe how resonant interactions with poloidal and toroidal components of the ULF waves can change the electron\textquoterights energy and provide radial displacements. We also present radial diffusion and guiding center simulations that show the importance of radial transpor ... SHPRITS, Y; ELKINGTON, S; MEREDITH, N; SUBBOTIN, D; Published by: Journal of Atmospheric and SolarTerrestrial Physics Published on: 11/2008 YEAR: 2008 DOI: 10.1016/j.jastp.2008.06.008 
2007 
Slot region electron loss timescales due to plasmaspheric hiss and lightninggenerated whistlers [1] Energetic electrons (E > 100 keV) in the Earth\textquoterights radiation belts undergo Dopplershifted cyclotron resonant interactions with a variety of whistler mode waves leading to pitch angle scattering and subsequent loss to the atmosphere. In this study we assess the relative importance of plasmaspheric hiss and lightninggenerated whistlers in the slot region and beyond. Electron loss timescales are determined using the Pitch Angle and energy Diffusion of Ions and Electrons (PADIE) code with global models of the s ... Meredith, Nigel; Horne, Richard; Glauert, Sarah; Anderson, Roger; Published by: Journal of Geophysical Research Published on: 08/2007 YEAR: 2007 DOI: 10.1029/2007JA012413 
[1] Energetic electrons (>=50 keV) are injected into the slot region (2 < L < 4) between the inner and outer radiation belts during the early recovery phase of geomagnetic storms. Enhanced convection from the plasma sheet can account for the stormtime injection at lower energies but does not explain the rapid appearance of higherenergy electrons (>=150 keV). The effectiveness of either radial diffusion (driven by enhanced ULF waves) or local acceleration (during interactions with enhanced whistler mode chorus emissions), a ... Thorne, R.; . Y. Shprits, Y; Meredith, N.; Horne, R.; Li, W.; Lyons, L.; Published by: Journal of Geophysical Research Published on: 06/2007 YEAR: 2007 DOI: 10.1029/2006JA012176 ShockInduced Transport. Slot Refilling and Formation of New Belts. 
Radiation belt electrons can interact with various modes of plasma wave in their drift orbits about the Earth, including whistlermode chorus outside the plasmasphere, and both whistlermode hiss and electromagnetic ion cyclotron waves inside the plasmasphere. Electrons undergo gyroresonant diffusion in their interactions with these waves. To determine the timescales for electron momentum diffusion and pitch angle diffusion, we develop bounceaveraged quasilinear resonant diffusion coefficients for fieldaligned electromagn ... Summers, D.; Ni, Binbin; Meredith, Nigel; Published by: Journal of Geophysical Research Published on: 04/2007 YEAR: 2007 DOI: 10.1029/2006JA011801 
2006 
Energetic outer zone electron loss timescales during low geomagnetic activity Following enhanced magnetic activity the fluxes of energetic electrons in the Earth\textquoterights outer radiation belt gradually decay to quiettime levels. We use CRRES observations to estimate the energetic electron loss timescales and to identify the principal loss mechanisms. Gradual loss of energetic electrons in the region 3.0 <= L <= 5.0 occurs during quiet periods (Kp < 3) following enhanced magnetic activity on timescales ranging from 1.5 to 3.5 days for 214 keV electrons to 5.5 to 6.5 days for 1.09 MeV electrons ... Meredith, Nigel; Horne, Richard; Glauert, Sarah; Thorne, Richard; Summers, D.; Albert, Jay; Anderson, Roger; Published by: Journal of Geophysical Research Published on: 05/2006 YEAR: 2006 DOI: 10.1029/2005JA011516 
Phase space density analysis of the outer radiation belt energetic electron dynamics We present an analysis of the electron phase space density in the Earth\textquoterights outer radiation belt during three magnetically disturbed periods to determine the likely roles of inward radial diffusion and local acceleration in the energization of electrons to relativistic energies. During the recovery phase of the 9 October 1990 storm and the period of prolonged substorms between 11 and 16 September 1990, the relativistic electron phase space density increases substantially and peaks in the phase space density occur ... Iles, Roger; Meredith, Nigel; Fazakerley, Andrew; Horne, Richard; Published by: Journal of Geophysical Research Published on: 03/2006 YEAR: 2006 DOI: 10.1029/2005JA011206 
2005 
Wave acceleration of electrons in the Van Allen radiation belts The Van Allen radiation belts1 are two regions encircling the Earth in which energetic charged particles are trapped inside the Earth\textquoterights magnetic field. Their properties vary according to solar activity2, 3 and they represent a hazard to satellites and humans in space4, 5. An important challenge has been to explain how the charged particles within these belts are accelerated to very high energies of several million electron volts. Here we show, on the basis of the analysis of a rare event where the outer radiati ... Horne, Richard; Thorne, Richard; Shprits, Yuri; Meredith, Nigel; Glauert, Sarah; Smith, Andy; Kanekal, Shrikanth; Baker, Daniel; Engebretson, Mark; Posch, Jennifer; Spasojevic, Maria; Inan, Umran; Pickett, Jolene; Decreau, Pierrette; Published by: Nature Published on: 09/2005 YEAR: 2005 DOI: 10.1038/nature03939 
2003 
We examine signatures of two types of waves that may be involved in the acceleration of energetic electrons in Earth\textquoterights outer radiation belts. We have compiled a database of ULF wave power from SAMNET and IMAGE ground magnetometer stations for 1987\textendash2001. Longduration, comprehensive, in situ VLF/ELF chorus wave observations are not available, so we infer chorus wave activity from lowaltitude SAMPEX observations of MeV electron microbursts for 1996\textendash2001 since microbursts are thought to be cau ... O\textquoterightBrien, T.; Lorentzen, K.; Mann, I.; Meredith, N.; Blake, J.; Fennell, J.; Looper, M.; Milling, D.; Anderson, R.; Published by: Journal of Geophysical Research Published on: 08/2003 YEAR: 2003 DOI: 10.1029/2002JA009784 
We perform a survey of the plasma wave and particle data from the CRRES satellite during 26 geomagnetically disturbed periods to investigate the viability of a local stochastic electron acceleration mechanism to relativistic energies driven by Dopplershifted cyclotron resonant interactions with whistler mode chorus. Relativistic electron flux enhancements associated with moderate or strong storms may be seen over the whole outer zone (3 < L < 7), typically peaking in the range 4 < L < 5, whereas those associated with weak s ... Meredith, Nigel; Cain, Michelle; Horne, Richard; Thorne, Richard; Summers, D.; Anderson, Roger; Published by: Journal of Geophysical Research Published on: 06/2003 YEAR: 2003 DOI: 10.1029/2002JA009764 
Electromagnetic ion cyclotron (EMIC) waves which propagate at frequencies below the proton gyrofrequency can undergo cyclotron resonant interactions with relativistic electrons in the outer radiation belt and cause pitchangle scattering and electron loss to the atmosphere. Typical stormtime wave amplitudes of 1\textendash10 nT cause strong diffusion scattering which may lead to significant relativistic electron loss at energies above the minimum energy for resonance, Emin. A statistical analysis of over 800 EMIC wave event ... Published by: Journal of Geophysical Research Published on: 06/2003 YEAR: 2003 DOI: 10.1029/2002JA009700 
2000 
The temporal evolution of electron distributions and associated wave activity following substorm injections in the inner magnetosphere are investigated using data from the CRRES satellite. Equatorial electron distributions and concomitant wave spectra outside the plasmapause on the nightside of the Earth are studied as a function of time since injection determined from the auroralelectrojet index (AE). The electron cyclotron harmonic (ECH) wave amplitudes are shown to be very sensitive to small modeling errors in the locati ... Meredith, Nigel; Horne, Richard; Johnstone, Alan; Anderson, Roger; Published by: Journal of Geophysical Research Published on: 06/2000 YEAR: 2000 DOI: 10.1029/2000JA900010 
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