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In this study, we present Van Allen Probe observations showing that seed (hundreds of keV) and core (≳ 1 MeV) electrons can resonate with ultra‐low‐frequency (ULF) wave modes with distinctive m values simultaneously. An unusual electron energy spectrogram with double‐banded resonant structure was recorded by energetic particle, composition, and thermal plasma (ECT)‐magnetic electron ion spectrometer (MagEIS) and, meanwhile, boomerang stripes in pitch angle spectrogram appeared at the lower energy band. A localized drift resonance with m = 10 wave component was responsible for the resonant band peaked at ∼200 keV while a global drift resonance with m = 3 component gave rise to the upper band resonance peaked at ∼1 MeV. Time‐Of‐Flight on boomerang stripes suggested that the localized drift resonance with ∼200 keV electrons was confined within the plasmaspheric plume. Electron flux modulations were reproduced by numerical simulations in good consistency with the observations, supporting the scenario that localized and global drift resonance could coexist in the outer belt electron dynamics simultaneously. Key Points: We, for the first time, report the banded drift resonance between outer belt electrons and ULF wavesULF waves with small and moderate azimuthal wave numbers can resonate with core and seed electrons simultaneouslyAzimuthally localized and global drift resonances are able to coexist [ABSTRACT FROM AUTHOR]

In this study we focus on the radiation belt dynamics driven by the geomagnetic storms during September 2017. Besides the long-lasting three-belt structures of ultrarelativistic electrons (>2 MeV, existing for tens of days), which has been studied intensively during the Van Allen Probe era, it is found that magnetospheric electrons of hundreds of keVs can also have three-belt structures at similar L extent during storm time. Measurements of 500-800 keV electrons from MagEIS instrument onboard Van Allen Probes show double-peaked (L = 3.5 and 4.5, respectively) flux-versus-L-shell profile in the outer belt, which lasted for 2-3 days. During the time interval of such transient three-belt structure, the energy-versus-L spectrogram shows novel distributions differing from both "S-shaped" and "V-shaped" spectrograms reported previously. Such peculiar distribution also illustrates the energy-dependent occurrence of the three-belt profile. The gradual formation of "reversed energy spectrum" at L~3.5 also indicates that hiss scattering inside the plasmapause contributed to the fast decay of sub-MeV remnant belt. [ABSTRACT FROM AUTHOR]

Six years of Van Allen Probes data are used to investigate cold plasmaspheric electrons affected by ultralow‐frequency (ULF) waves in the inner magnetosphere (L<7) including spatial distributions, occurrence conditions, and resonant energy range. Events exhibit a global distribution within L= 4–7 but preferentially occur at L∼5.5–7 in the dayside, while there is higher occurrence rate in the duskside than dawnside. They can occur under different geomagnetic activities and solar wind velocities (VS), but the occurrence rates are increasing with larger AE, |SYMH|, and VS. These features are closely associated with the generation and propagation of ULF waves in Pc4 (45–150 s) and Pc5 (150–600 s) bands. Combined with electron observations from HOPE instrument, the resonant energies inferred from wave power indicate that cold electrons at ones to hundreds of electron volts can be affected by ULF waves. This study may shed new light on further investigations on the acceleration and transportation of cold plasmaspheric particles that would affect plasmaspheric material release to the Earth's magnetosphere and instabilities for exciting various waves. Key Points: Interactions between ULF waves and cold electrons occur at L = 4–7 with dominant distributions in the dayside and a dawn‐dusk asymmetryThe event occurrence rates are increasing with larger AE, |SYMH|, and solar wind velocityThe resonant energy inferred from wave power and electron observations indicates that electrons at ones to hundreds of electron volts are affected by ULF waves [ABSTRACT FROM AUTHOR]

Standing and traveling shear Alfvén waves contribute to electron acceleration and parallel electric field formation on auroral field lines in the Earth's magnetosphere. In this paper, the self-consistent coupled Vlasov-Maxwell system for shear Alfvén waves is solved in one dimension. The Vlasov equation is gyro-averaged in order to minimize the number of dimensions in the problem, and to avoid numerical problems with the direct evaluation of the parallel electric field, the electron distribution function is described in terms of a spatial coordinate along the field line, the magnetic moment, and the canonical parallel momentum per unit mass. Some preliminary studies of shear Alfvén wave pulses propagating in a uniform magnetic field on model auroral field lines are presented with an emphasis on the kinetic electron response and the parallel electric field. It is shown that when the full parallel electron dynamics are included, wave-particle interactions result in intensification of the parallel electric field and significant heating of the electrons. It is also demonstrated the acceleration of electrons to speeds of the order of twice the wave phase speed, which has been shown by previous calculations. The results are compared with recent observations made by both the NASA Fast Auroral Snapshot and the Freja satellites. [ABSTRACT FROM AUTHOR]

Abstract: The overarching objective of the ILWS Geospace program is to facilitate system level science. This demands synoptic observations such as global auroral imaging. At present, there is no funded mission during ILWS that incorporates a global auroral imager. The imaging community needs to move now to address this important gap. While doing so, it is interesting to take stock of global auroral observations that have not been achieved, or that have been achieved only to a limited extent. These include simultaneous imaging across all relevant scales, spectral resolution of sufficient quality to allow for global maps of characteristic energy and energy flux of precipitating electrons, continuous global auroral imaging for time periods spanning long-duration geomagnetic events, systematic interhemispheric conjugate observations, auroral observations magnetically conjugate to in situ measurements, and automatic classification of auroral images. These observations can be achieved within the next decade. If they are, then they will facilitate exciting new science. [Copyright &y& Elsevier]