Charged particle scattering in dipolarized magnetotail

Lukin, A. S.; Artemyev, А. V.; Petrukovich, A. A.; Zhang, X.-J.

doi:10.1063/5.0062160

Cited by 6 publications

(4 citation statements)

References 72 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“… 1994 ; Lukin et al. 2021 ). At ∼11:05:55 UT (shortly after, but still near the transition region between the plasma sheet and inner magnetosphere), ELFIN A observed a distinct, dispersive feature of the precipitating-to-trapped flux ratio: the lowest energy approaching the ratio of increased with proximity to Earth (as -shell decreased), a trend marked by an inclined dotted arrow in the figure.…”

Section: Elfin Examples Of Emic Wave-driven Electron Precipitationmentioning

confidence: 99%

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

et al. 2023

Self Cite

View full text Add to dashboard Cite

We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or $\Delta L\sim 0.56$ Δ L ∼ 0.56 ) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at $L\sim 5-7$ L ∼ 5 − 7 at dusk, while a smaller subset exists at $L\sim 8-12$ L ∼ 8 − 12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an $L$ L -shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of $\sim 1.45$ ∼ 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

show abstract

Section: Elfin Examples Of Emic Wave-driven Electron Precipitationmentioning

confidence: 99%

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…This precipitation was thus observed by ELFIN in the relatively higher-latitude region. During 06:56:30-06:57:15 UT, as the spacecraft flew into rela-tively lower-latitude ionospheric regions where the corresponding equatorial magnetic fields are stronger and more dipolarized (i.e., B z increases and ∂B x /z decreases), the magnetic field curvature radius is increased (Sergeev et al, 1983;Lukin et al, 2021). Thus, we do not see precipitation driven by field-line curvature scattering in this region.…”

Section: Observationsmentioning

confidence: 80%

Tens to hundreds of keV electron precipitation driven by kinetic Alfvén waves during an electron injection

Shen,

Artemyev,

Zhang

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Electron injections are critical processes associated with magnetospheric substorms, which deposit significant electron energy into the ionosphere. Although wave scattering of < 10 keV electrons during injections has been well studied, the link between magnetotail electron injections and energetic (≥ 100 keV) electron precipitation remains elusive. Using conjugate observations between the ELFIN and Magnetospheric Multiscale (MMS) missions, we present evidence of tens to hundreds of keV electron precipitation to the ionosphere potentially driven by kinetic Alfvén waves (KAWs) associated with magnetotail electron injections and magnetic field gradients. Test particle simulations adapted to observations show that dipolarization-front magnetic field gradients and associated ∇B drifts allow Doppler-shifted Landau resonances between the injected electrons and KAWs, producing electron spatial scattering across the front which results in pitch-angle decreases and subsequent precipitation. Test particle results show that such KAW-driven precipitation can account for ELFIN observations below ∼300 keV.

show abstract

“…This flux increase is also associated with a high ratio j loss / j trap ∼ 1 showing strong energy dispersion: larger energies with j loss / j trap ∼ 1 are closer to the Earth (see Figures 12c and 12d). This pattern most likely corresponds to the electron isotropic boundary (Imhof et al., 1979; Sergeev et al., 2012; Yahnin et al., 1997), that is, energetic electron scattering in the current sheet due to the magnetic field line curvature (Birmingham, 1984; Büchner & Zelenyi, 1989; Lukin, Artemyev, Petrukovich, & Zhang, 2021; Young et al., 2002). The curvature scattering efficiency depends on energy and the equatorial magnetic field curvature radius and intensity.…”

Section: Examples Of Dipolarizing Flux Bundlesmentioning

confidence: 99%

On the Role of Whistler‐Mode Waves in Electron Interaction With Dipolarizing Flux Bundles

2022

Self Cite

View full text Add to dashboard Cite

The magnetotail is the main source of energetic electrons for Earth’s inner magnetosphere. Electrons are adiabatically heated during flow bursts (rapid earthward motion of the plasma) within dipolarizing flux bundles (concurrent increases and dipolarizations of the magnetic field). The electron heating is evidenced near or within dipolarizing flux bundles as rapid increases in the energetic electron flux (10–100 keV); it is often referred to as injection. The anisotropy in the injected electron distributions, which is often perpendicular to the magnetic field, generates whistler‐mode waves, also commonly observed around such dipolarizing flux bundles. Test‐particle simulations reproduce several features of injections and electron adiabatic dynamics. However, the feedback of the waves on the electron distributions has been not incorporated into such simulations. This is because it has been unclear, thus far, whether incorporating such feedback is necessary to explain the evolution of the electron pitch‐angle and energy distributions from their origin, reconnection ejecta in the mid‐tail region, to their final destination, and the electron injection sites in the inner magnetosphere. Using an analytical model we demonstrate that wave feedback is indeed important for the evolution of electron distributions. Combining canonical guiding center theory and the mapping technique we model electron adiabatic heating and scattering by whistler‐mode waves around a dipolarizing flux bundle. Comparison with spacecraft observations allows us to validate the efficacy of the proposed methodology. Specifically, we demonstrate that electron resonant interactions with whistler‐mode waves can indeed change markedly the pitch‐angle distribution of energetic electrons at the injection site and are thus critical to incorporate in order to explain the observations. We discuss the importance of such resonant interactions for injection physics and for magnetosphere‐ionosphere coupling.

show abstract

Charged particle scattering in dipolarized magnetotail

Cited by 6 publications

References 72 publications

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

Energetic Electron Precipitation Driven by Electromagnetic Ion Cyclotron Waves from ELFIN’s Low Altitude Perspective

Tens to hundreds of keV electron precipitation driven by kinetic Alfvén waves during an electron injection

On the Role of Whistler‐Mode Waves in Electron Interaction With Dipolarizing Flux Bundles

Contact Info

Product

Resources

About