Found 17 entries in the Bibliography.

Showing entries from 1 through 17


Dynamic evolution of energetic outer zone electrons due to wave-particle interactions during storms

[1] Relativistic electrons in the outer radiation belt are subjected to pitch angle and energy diffusion by chorus, electromagnetic ion cyclotron (EMIC), and hiss waves. Using quasi-linear diffusion coefficients for cyclotron resonance with field-aligned waves, we examine whether the resonant interactions with chorus waves produce a net acceleration or loss of relativistic electrons. We also examine the effect of pitch angle scattering by EMIC and hiss waves during the main and recovery phases of a storm. The numerical simul ...

Li, W.; . Y. Shprits, Y; Thorne, R.;

YEAR: 2007     DOI: 10.1029/2007JA012368

Local Loss due to VLF/ELF/EMIC Waves

Slot region electron loss timescales due to plasmaspheric hiss and lightning-generated whistlers

[1] Energetic electrons (E > 100 keV) in the Earth\textquoterights radiation belts undergo Doppler-shifted 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 lightning-generated 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;

YEAR: 2007     DOI: 10.1029/2007JA012413

Local Loss due to VLF/ELF/EMIC Waves

Review of radiation belt relativistic electron losses

We present a brief review of radiation belt electron losses which are vitally important for controlling the dynamics of the radiation belts. A historical overview of early observations is presented, followed by a brief description of important known electron loss mechanisms. We describe key theoretical results and observations related to pitch-angle scattering by resonant interaction with plasmaspheric hiss, whistler-mode chorus and electromagnetic ion cyclotron waves, and review recent work on magnetopause losses. In partic ...


YEAR: 2007     DOI: 10.1016/j.jastp.2006.06.019

Local Loss due to VLF/ELF/EMIC Waves


Observation of two distinct, rapid loss mechanisms during the 20 November 2003 radiation belt dropout event

The relativistic electron dropout event on 20 November 2003 is studied using data from a number of satellites including SAMPEX, HEO, ACE, POES, and FAST. The observations suggest that the dropout may have been caused by two separate mechanisms that operate at high and low L-shells, respectively, with a separation at L \~ 5. At high L-shells (L > 5), the dropout is approximately independent of energy and consistent with losses to the magnetopause aided by the Dst effect and outward radial diffusion which can deplete relativis ...

Bortnik, J.; Thorne, R.; O\textquoterightBrien, T.; Green, J.; Strangeway, R.; . Y. Shprits, Y; Baker, D.;

YEAR: 2006     DOI: 10.1029/2006JA011802

Local Loss due to VLF/ELF/EMIC Waves

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 quiet-time 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;

YEAR: 2006     DOI: 10.1029/2005JA011516

Local Loss due to VLF/ELF/EMIC Waves


Timescale for MeV electron microburst loss during geomagnetic storms

Energetic electrons in the outer radiation belt can resonate with intense bursts of whistler-mode chorus emission leading to microburst precipitation into the atmosphere. The timescale for removal of outer zone MeV electrons during the main phase of the October 1998 magnetic storm has been computed by comparing the rate of microburst loss observed on SAMPEX with trapped flux levels observed on Polar. Effective lifetimes are comparable to a day and are relatively independent of L shell. The lifetimes have also been evaluated ...

Thorne, R.; O\textquoterightBrien, T.; . Y. Shprits, Y; Summers, D.; Horne, R.;

YEAR: 2005     DOI: 10.1029/2004JA010882

Local Loss due to VLF/ELF/EMIC Waves


Quantification of relativistic electron microburst losses during the GEM storms

Bursty precipitation of relativistic electrons has been implicated as a major loss process during magnetic storms. One type of precipitation, microbursts, appears to contain enough electrons to empty the prestorm outer radiation belt in approximately a day. During storms that result in high fluxes of trapped relativistic electrons, microbursts continue for several days into the recovery phase, when trapped fluxes are dramatically increasing. The present study shows that this apparent inconsistency is resolved by observations ...

O\textquoterightBrien, T.; Looper, M.; Blake, J.;

YEAR: 2004     DOI: 10.1029/2003GL018621

Local Loss due to VLF/ELF/EMIC Waves


Evaluation of quasi-linear diffusion coefficients for EMIC waves in a multispecies plasma

Quasi-linear velocity-space diffusion coefficients due to L-mode electromagnetic ion cyclotron (EMIC) waves are considered in a multispecies plasma. It is shown, with slight approximations to exact cold plasma theory, that within EMIC pass bands the index of refraction is a monotonically increasing function of frequency. Analytical criteria are then derived which identify ranges of latitude, wavenormal angle, and resonance number consistent with resonance in a prescribed wave population. This leads to computational technique ...

Albert, J.;

YEAR: 2003     DOI: 10.1029/2002JA009792

Local Loss due to VLF/ELF/EMIC Waves

Statistical analysis of relativistic electron energies for cyclotron resonance with EMIC waves observed on CRRES

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 pitch-angle scattering and electron loss to the atmosphere. Typical storm-time 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 ...

Meredith, Nigel;

YEAR: 2003     DOI: 10.1029/2002JA009700

Local Loss due to VLF/ELF/EMIC Waves

Relativistic electron acceleration and precipitation during resonant interactions with whistler-mode chorus

1] Resonant interactions with whistler-mode chorus waves provide an important process for electron loss and acceleration during storm times. We demonstrate that wave propagation significantly affects the electron scattering rates. We show that stormtime chorus waves outside the plasmapause can scatter equatorial electrons <=60 keV into the loss cone and accelerate trapped electrons up to \~ MeV energies at large pitch-angles. Using ray tracing to map the waves to higher latitudes, we show that the decrease in the ratio betwe ...

Horne, R.;

YEAR: 2003     DOI: 10.1029/2003GL016973

Local Loss due to VLF/ELF/EMIC Waves

Relativistic electron pitch-angle scattering by electromagnetic ion cyclotron waves during geomagnetic storms

[1] During magnetic storms, relativistic electrons execute nearly circular orbits about the Earth and traverse a spatially confined zone within the duskside plasmapause where electromagnetic ion cyclotron (EMIC) waves are preferentially excited. We examine the mechanism of electron pitch-angle diffusion by gyroresonant interaction with EMIC waves as a cause of relativistic electron precipitation loss from the outer radiation belt. Detailed calculations are carried out of electron cyclotron resonant pitch-angle diffusion coef ...

Summers, D.;

YEAR: 2003     DOI: 10.1029/2002JA009489

Local Loss due to VLF/ELF/EMIC Waves


X-ray observations of MeV electron precipitation with a balloon-borne germanium spectrometer

The high-resolution germanium detector aboard the MAXIS (MeV Auroral X-ray Imaging and Spectroscopy) balloon payload detected nine X-ray bursts with significant flux extending above 0.5 MeV during an 18 day flight over Antarctica. These minutes-to-hours-long events are characterized by an extremely flat spectrum (\~E-2) similar to the first MeV event discovered in 1996, indicating that the bulk of parent precipitating electrons is at relativistic energies. The MeV bursts were detected between magnetic latitudes 58\textdegree ...

Millan, R.;

YEAR: 2002     DOI: 10.1029/2002GL015922

Local Loss due to VLF/ELF/EMIC Waves


Electron scattering loss in Earth\textquoterights inner magnetosphere 1. Dominant physical processes

Pitch angle diffusion rates due to Coulomb collisions and resonant interactions with plasmaspheric hiss, lightning-induced whistlers and anthropogenic VLF transmissions are computed for inner magnetospheric electrons. The bounce-averaged, quasi-linear pitch angle diffusion coefficients are input into a pure pitch angle diffusion equation to obtain L and energy dependent equilibrium distribution functions and precipitation lifetimes. The relative effects of each scattering mechanism are considered as a function of electron en ...

Abel, Bob; Thorne, Richard;

YEAR: 1998     DOI: 10.1029/97JA02919

Local Loss due to VLF/ELF/EMIC Waves


Equilibrium Structure of Radiation Belt Electrons

The detailed quiet time structure of energetic electrons in the earth\textquoterights radiation belts is explained on the basis of a balance between pitch angle scattering loss and inward radial diffusion from an average outer zone source. Losses are attributed to a combination of classical Coulomb scattering at low L and whistler mode turbulent pitch angle diffusion throughout the outer plasmasphere. Radial diffusion is driven by substorm associated fluctuations of the magnetospheric convection electric field.

Lyons, Lawrence; Thorne, Richard;

YEAR: 1973     DOI: 10.1029/JA078i013p02142

Local Loss due to VLF/ELF/EMIC Waves


Parasitic Pitch Angle Diffusion of Radiation Belt Particles by Ion Cyclotron Waves

The resonant pitch angle scattering of protons and electrons by ion cyclotron turbulence is investigated. The analysis is analogous to that recently performed for electron interactions with whistler mode waves. The role played by the intense band of ion cyclotron waves, predicted to be generated just within the plasmapause during the decay of the magnetospheric ring current, is evaluated in detail. Loss rates resulting from parasitic interactions with this turbulence are determined for energetic protons and relativistic elec ...

Lyons, Lawrence; Thorne, Richard;

YEAR: 1972     DOI: 10.1029/JA077i028p05608

Local Loss due to VLF/ELF/EMIC Waves


Velocity Space Diffusion from Weak Plasma Turbulence in a Magnetic Field

The quasi-linear velocity space diffusion is considered for waves of any oscillation branch propagating at an arbitrary angle to a uniform magnetic field in a spatially uniform plasma. The space-averaged distribution function is assumed to change slowly compared to a gyroperiod and characteristic times of the wave motion. Nonlinear mode coupling is neglected. An H-like theorem shows that both resonant and nonresonant quasi-linear diffusion force the particle distributions towards marginal stablity. Creation of the marginally ...

Kennel, C.;

YEAR: 1966     DOI: 10.1063/1.1761629

Local Loss due to VLF/ELF/EMIC Waves

Limit on Stably Trapped Particle Fluxes

Whistler mode noise leads to electron pitch angle diffusion. Similarly, ion cyclotron noise couples to ions. This diffusion results in particle precipitation into the ionosphere and creates a pitch angle distributon of trapped particles that is unstable to further wave growth. Since excessive wave growth leads to rapid diffusion and particle loss, the requirement that the growth rate be limited to the rate at which wave energy is depleted by wave propagation permits an estimate of an upper limit to the trapped equatorial par ...

Kennel, C.; Petschek, H.;

YEAR: 1966     DOI: 10.1029/JZ071i001p00001

Local Loss due to VLF/ELF/EMIC Waves