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The importance of ElectroMagnetic Ion Cyclotron (EMIC) ultra-low-frequency (ULF) waves (and their Pc1 counterparts) is connected to their critical role in triggering energetic particle precipitation from the magnetosphere to the conjugated ionosphere via pitch angle scattering. In addition, as a prominent element of the ULF zoo, EMIC/Pc1 waves can be considered a perfect tool for the remote diagnosis of the topologies and dynamic properties of near-Earth plasmas. Based on the availability of a comprehensive set of instruments, operating on the ground and in the top-side ionosphere, the present case study provides an interesting example of the evolution of EMIC propagation to both ionospheric hemispheres up to the polar cap. Specifically, we report observations of Pc1 waves detected on 30 March 2021 under low Kp, low Sym-H, and moderate AE conditions. The proposed investigation shows that high-latitude ground magnetometers in both hemispheres and the first China Seismo-Electromagnetic Satellite (CSES-01) at a Low Earth Orbit (LEO) detected in-synch Pc1 waves. In strict correspondence to this, energetic proton precipitation was observed at LEO with a simultaneous appearance of an isolated proton aurora at subauroral latitudes. This supports the idea of EMIC wave-induced proton precipitation contributing to energy transfer from the magnetosphere to the ionosphere.
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Interhemispheric Observations of ULF Waves Caused by Foreshock Transients Under Quiet Solar Wind Conditions
Key Points Magnetospheric Multiscale observed a series of foreshock transients near the Earth's bow shock Pc1 waves and magnetic impulse events are observed by ground magnetometers in both hemispheres following the foreshock transients The difference in observation times between hemispheres implies that Pc1 waves are generated in the off‐equatorial region
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- PAR ID:
- 10465510
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 128
- Issue:
- 9
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Thermalization and heating of plasma flows at shocks result in unstable charged-particle distributions that generate a wide range of electromagnetic waves. These waves, in turn, can further accelerate and scatter energetic particles. Thus, the properties of the waves and their implication for wave−particle interactions are critically important for modeling energetic particle dynamics in shock environments. Whistler-mode waves, excited by the electron heat flux or a temperature anisotropy, arise naturally near shocks and foreshock transients. As a result, they can often interact with suprathermal electrons. The low background magnetic field typical at the core of such transients and the large wave amplitudes may cause such interactions to enter the nonlinear regime. In this study, we present a statistical characterization of whistler-mode waves at foreshock transients around Earth’s bow shock, as they are observed under a wide range of upstream conditions. We find that a significant portion of them are sufficiently intense and coherent (narrowband) to warrant nonlinear treatment. Copious observations of background magnetic field gradients and intense whistler wave amplitudes suggest that phase trapping, a very effective mechanism for electron acceleration in inhomogeneous plasmas, may be the cause. We discuss the implications of our findings for electron acceleration in planetary and astrophysical shock environments.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2023JA031596
