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Abstract Energetic electron losses in the Earth's inner magnetosphere are dominated by outward radial diffusion and scattering into the atmosphere by various electromagnetic waves. The two most important wave modes responsible for electron scattering are electromagnetic ion cyclotron (EMIC) waves and whistler‐mode waves (whistler waves) that, acting together, can provide rapid electron losses over a wide energy range from few keV to few MeV. Wave‐particle resonant interaction resulting in electron scattering is well described by quasi‐linear diffusion theory using the cold plasma dispersion, whereas the effects of nonlinear resonances and hot plasma dispersion are less well understood. This study aims to examine these effects and estimate their significance for a particular event during which both wave modes are quasi‐periodically modulated by ultra‐low‐frequency (ULF) compressional waves. Such modulation of EMIC and whistler wave amplitudes provides a unique opportunity to compare nonlinear resonant scattering (important for the most intense waves) with quasi‐linear diffusion (dominant for low‐intensity waves). The same modulation of plasma properties allows better characterization of hot plasma effects on the EMIC wave dispersion. Although hot plasma effects significantly increase the minimum resonant energy,Emin, for the most intense EMIC waves, such effects become negligible for the higher frequency part of the hydrogen‐band EMIC wave spectrum. Nonlinear phase trapping of 300–500 keV electrons through resonances with whistler waves may accelerate and make them resonant with EMIC waves that, in turn, quickly scatter those electrons into the loss‐cone. Our results highlight the importance of nonlinear effects for simulations of energetic electron fluxes in the inner magnetosphere.
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FDTD Simulations Of The Impedance Of A Dipole Antenna in A Plasma
The impedance of a dipole antenna in the earth’s ionospheric plasma is dependent on the ambient plasma properties such as electron density and electron neutral collision frequency. Depending on the length of the dipole, it is possible to not only measure the plasma properties, but in addition, receive plasma waves that are found propagating in the ionosphere. Here we report on some FDTD simulations of a dipole antenna in a cold plasma, and present some approximate expressions that can be used to analyze this behavior. When the dipole antenna resonant wavelength /4 and associated frequency is far from the upper hybrid, cyclotron and plasma frequencies of the local plasma, the expressions work fairly well. However, when the length of the antenna is such that it’s resonant wavelength coincides or is close to the plasma resonances, the expressions fail, and a full-wave FDTD simulation has to be performed to extract meaningful plasma data.
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- Award ID(s):
- 1655280
- PAR ID:
- 10145386
- Date Published:
- Journal Name:
- 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting
- Page Range / eLocation ID:
- 1661 to 1662
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/APUSNCURSINRSM.2019.8888864
