Magnetic Field Variations and Dynamics of the Outer Electron Radiation Belt of the Earth’s Magnetosphere in February 2014

Vlasova, N. A.; Калегаев, В. В.; Nazarkov, Ilya; Prost, Arnaud

doi:10.1134/s0016793220010144

Cited by 9 publications

(6 citation statements)

References 19 publications

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“…Present radiation belt models are empirically parameterized by temporal and spatial averages of wave properties, using multi-year spacecraft observations (e.g., Agapitov et al, 2013;Li, Ma, et al, 2015;Malaspina et al, 2017;Meredith et al, 2012). The use of such averages is justified by the commonly used quasi-linear diffusion theory, which describes wave-particle interactions based on the assumption of a turbulent spectrum of low-amplitude waves, for which the average wave intensity is a sufficiently good measure (Andronov & Trakhtengerts, 1964;Kennel & Engelmann, 1966;Lyons et al, 1972). Transient populations of intense waves that can interact with the electrons nonlinearly, may be smoothed out in such averages and not represented in empirical wave models.…”

Section: Introductionmentioning

confidence: 99%

Relativistic Electron Precipitation Driven by Mesoscale Transients, Inferred From Ground and Multi‐Spacecraft Platforms

Artemyev,

Zhang,

Demekhov

et al. 2024

JGR Space Physics

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Precipitation of relativistic electrons into the Earth's atmosphere regulates the outer radiation belt fluxes and contributes to magnetosphere‐atmosphere coupling. One of the main drivers of such precipitation is electron scattering by whistler‐mode waves. Such waves typically originate at the equator, where they can resonate with and scatter sub‐relativistic (tens to a few hundred keV) electrons. However, they can occasionally propagate far away from the equator along field lines, reaching middle latitudes, where they can resonate with and scatter relativistic (>500 keV) electrons. Such a propagation is typical for the dayside, but statistically has not been found on the nightside where the waves are quickly damped along their propagation due to Landau damping. Here we explore two events of relativistic electron precipitation from low‐altitude observations on the nightside. Combining measurements of whistler‐mode waves from ground observatories, relativistic electron precipitation from low‐altitude satellites, total electron content maps from GPS receivers, and magnetic field and electron flux from equatorial satellites, we show wave ducting by plasma density gradients is the possible channel that allows the waves to reach middle latitudes and scatter relativistic electrons. We suggest that both whistler‐mode wave generation and ducting can be driven by equatorial mesoscale (with spatial scales of about one Earth radius) transient structures during nightside injections. We also compare these nightside events with observations of ducted waves and relativistic electron precipitation at the dayside, where wave generation and ducting are driven by ultra‐low‐frequency waves. This study demonstrates the potential importance of mesoscale transients in relativistic electron precipitation, but does not however unequivocally establish that ducted whistler‐mode waves are the primary cause of the observed electron precipitation.

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Section: Introductionmentioning

confidence: 99%

Relativistic Electron Precipitation Driven by Mesoscale Transients, Inferred From Ground and Multi‐Spacecraft Platforms

Artemyev,

Zhang,

Demekhov

et al. 2024

JGR Space Physics

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“…

Since the 1960s, theoretical work has firmly established that resonant electron interactions with such waves represent an important mechanism of electron pitch angle scattering and subsequent loss to the atmosphere (Andronov & Trakhtengerts, 1964;Kennel & Petschek, 1966;Thorne & Kennel, 1971). Such scattering has been considered to be a major driver of electron losses across a wide range of energies including energetic and relativistic precipitation bands (hundreds of keV to MeV; see, e.g., Blake &

…”

mentioning

confidence: 99%

Relativistic Electron Precipitation Driven by Nonlinear Resonance With Whistler‐Mode Waves

et al. 2022

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Electron losses from the outer radiation belt are typically attributed to resonant electron scattering by whistler‐mode waves. Although the quasi‐linear diffusive regime of such scattering is well understood, the observed waves are often quite intense and in the nonlinear regime of resonant wave‐particle interaction. Such nonlinear resonant interactions are still being actively studied due to their potential for driving fast precipitation. However, direct observations of nonlinear resonance of whistler‐mode waves with electron distributions are scarce. Here, we present evidence for such resonance with high‐resolution electron energy and pitch angle spectra acquired at low‐altitudes by the dual Electron Losses and Fields INvestgation (ELFIN) CubeSats combined with conjugate measurements of equatorial plasma parameters, wave properties, and electron energy spectra by the Time History of Events and Macroscale Interactions during Substorms and Magnetospheric MultiScale missions. ELFIN has obtained numerous conjunction events exhibiting whistler wave driven precipitation; in this study, we present two such events which epitomize signatures of nonlinear resonant scattering. A test particle simulation of electron interactions with intense whistler‐mode waves prescribed at the equator is employed to directly compare modeled precipitation spectra with ELFIN observations. We show that the observed precipitating spectra match expectations to within observational uncertainties of wave amplitude for reasonable assumptions of wave power distribution along the magnetic field line. These results indicate the importance of nonlinear resonant effects when describing intense precipitation patterns of energetic electrons and open the possibility of remotely investigating equatorial wave properties using just properties of precipitation energy and pitch angle spectra.

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“…High amplitude whistler-mode chorus waves B = 1 nT, E > 50 mV/m are detected in the radiation belts. Hot (1-50 keV) electron populations with a temperature anisotropy are injected from the plasma sheet during substorms and are believed to provide the necessary free energy source for chorus wave excitation via linear and nonlinear processes (Andronov & Trakhtengerts, 1964). Bortnik et al (2009) correlated chorus waves at L = 6, with hiss at L = 2.8, with a 2-7 s lag in his generation.…”

Section: Vlf and The Radiation Beltsmentioning

confidence: 99%

The Seasonality of VLF Attenuation Through the Ionosphere Verified by DEMETER Satellite

Greninger

Colman

2021

JGR Space Physics

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We constructed a program, we call “Iriatten,” to calculate using parameters from the International Reference Ionosphere, attenuation of Very Low Frequency (VLF) radiation transiting the ionosphere. The calculations are performed as function of latitude, longitude, year, month, day, and hour and based upon the quasi‐longitudinal approximation put forth by Helliwell, where the wave vector k, is in the direction of propagation, and follows the Earth's magnetic field lines. The best values of various parameters are taken from the literature. Attenuation occurs through electron neutral collisions. In his seminal 1965 text, Helliwell presented atmospheric attenuation curves for day and night, 2 and 20 kHz, as a function of latitude. Program Iriatten is used to re‐calculate Helliwell's curves and then to fully exercise access to seasonality. High power VLF transmitters are utilized as a reference signal and two physical models are used to represent them. In the Vertically Inclined model, the attenuation is assumed to occur “straight up” from the location of the VLF transmitter. In the Crary model waves are launched from a dipole source and ionospheric attenuation is applied where the wave is turned up in the Earth‐ionospheric waveguide. Both representations reveal a seasonality that is unmistakable. Using the two models the ionospheric attenuation is calculated for four VLF transmitters and compared to observations by the DEMETER. Results from the Crary transmitter model more realistically portray seasonal variations exemplified by DEMETER satellite data. Crary model errors, which are within 11 dB, are lower than or comparable to Vertically Inclined errors.

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Magnetic Field Variations and Dynamics of the Outer Electron Radiation Belt of the Earth’s Magnetosphere in February 2014

Cited by 9 publications

References 19 publications

Relativistic Electron Precipitation Driven by Mesoscale Transients, Inferred From Ground and Multi‐Spacecraft Platforms

Relativistic Electron Precipitation Driven by Mesoscale Transients, Inferred From Ground and Multi‐Spacecraft Platforms

Relativistic Electron Precipitation Driven by Nonlinear Resonance With Whistler‐Mode Waves

The Seasonality of VLF Attenuation Through the Ionosphere Verified by DEMETER Satellite

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