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Simulation of the energy distribution of relativistic electron precipitation caused by quasi-linear interactions with EMIC waves.

Li Z, Millan RM, Hudson MK - J Geophys Res Space Phys (2013)

Bottom Line: The precipitating flux, on the other hand, first rapidly increases and then gradually decreases.We also show that increasing wave frequency can lead to the occurrence of a second peak.In both single- and double-peak cases, increasing wave frequency, cold plasma density or decreasing background magnetic field strength lowers the energies of the peak(s) and causes the precipitation to increase at low energies and decrease at high energies at the start of the precipitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, Dartmouth College Hanover, New Hampshire, USA.

ABSTRACT

[1]Previous studies on electromagnetic ion cyclotron (EMIC) waves as a possible cause of relativistic electron precipitation (REP) mainly focus on the time evolution of the trapped electron flux. However, directly measured by balloons and many satellites is the precipitating flux as well as its dependence on both time and energy. Therefore, to better understand whether pitch angle scattering by EMIC waves is an important radiation belt electron loss mechanism and whether quasi-linear theory is a sufficient theoretical treatment, we simulate the quasi-linear wave-particle interactions for a range of parameters and generate energy spectra, laying the foundation for modeling specific events that can be compared with balloon and spacecraft observations. We show that the REP energy spectrum has a peaked structure, with a lower cutoff at the minimum resonant energy. The peak moves with time toward higher energies and the spectrum flattens. The precipitating flux, on the other hand, first rapidly increases and then gradually decreases. We also show that increasing wave frequency can lead to the occurrence of a second peak. In both single- and double-peak cases, increasing wave frequency, cold plasma density or decreasing background magnetic field strength lowers the energies of the peak(s) and causes the precipitation to increase at low energies and decrease at high energies at the start of the precipitation.

No MeSH data available.


Related in: MedlinePlus

Bounce-averaged pitch angle diffusion coefficients for EMIC waves interacting with electrons of energies 0.1–5 MeV with an increment of 0.2 MeV and four different sets of wave and plasma parameters. Minimum resonant energies are indicated in the upper right corner of each graph.
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fig01: Bounce-averaged pitch angle diffusion coefficients for EMIC waves interacting with electrons of energies 0.1–5 MeV with an increment of 0.2 MeV and four different sets of wave and plasma parameters. Minimum resonant energies are indicated in the upper right corner of each graph.

Mentions: [7]Figure 1 shows the bounce-averaged diffusion coefficient as a function of equatorial pitch angles we calculated for 0.1–5 MeV electrons with four sets of equatorial background magnetic field strength B0, cold plasma density N0, and wave frequency ω. Each diffusion coefficient spans from 0° to an upper resonant pitch angle limit α0u and maximizes to a value 〈Dαα(α0,E)〉m at a pitch angle α0m.


Simulation of the energy distribution of relativistic electron precipitation caused by quasi-linear interactions with EMIC waves.

Li Z, Millan RM, Hudson MK - J Geophys Res Space Phys (2013)

Bounce-averaged pitch angle diffusion coefficients for EMIC waves interacting with electrons of energies 0.1–5 MeV with an increment of 0.2 MeV and four different sets of wave and plasma parameters. Minimum resonant energies are indicated in the upper right corner of each graph.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4497461&req=5

fig01: Bounce-averaged pitch angle diffusion coefficients for EMIC waves interacting with electrons of energies 0.1–5 MeV with an increment of 0.2 MeV and four different sets of wave and plasma parameters. Minimum resonant energies are indicated in the upper right corner of each graph.
Mentions: [7]Figure 1 shows the bounce-averaged diffusion coefficient as a function of equatorial pitch angles we calculated for 0.1–5 MeV electrons with four sets of equatorial background magnetic field strength B0, cold plasma density N0, and wave frequency ω. Each diffusion coefficient spans from 0° to an upper resonant pitch angle limit α0u and maximizes to a value 〈Dαα(α0,E)〉m at a pitch angle α0m.

Bottom Line: The precipitating flux, on the other hand, first rapidly increases and then gradually decreases.We also show that increasing wave frequency can lead to the occurrence of a second peak.In both single- and double-peak cases, increasing wave frequency, cold plasma density or decreasing background magnetic field strength lowers the energies of the peak(s) and causes the precipitation to increase at low energies and decrease at high energies at the start of the precipitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, Dartmouth College Hanover, New Hampshire, USA.

ABSTRACT

[1]Previous studies on electromagnetic ion cyclotron (EMIC) waves as a possible cause of relativistic electron precipitation (REP) mainly focus on the time evolution of the trapped electron flux. However, directly measured by balloons and many satellites is the precipitating flux as well as its dependence on both time and energy. Therefore, to better understand whether pitch angle scattering by EMIC waves is an important radiation belt electron loss mechanism and whether quasi-linear theory is a sufficient theoretical treatment, we simulate the quasi-linear wave-particle interactions for a range of parameters and generate energy spectra, laying the foundation for modeling specific events that can be compared with balloon and spacecraft observations. We show that the REP energy spectrum has a peaked structure, with a lower cutoff at the minimum resonant energy. The peak moves with time toward higher energies and the spectrum flattens. The precipitating flux, on the other hand, first rapidly increases and then gradually decreases. We also show that increasing wave frequency can lead to the occurrence of a second peak. In both single- and double-peak cases, increasing wave frequency, cold plasma density or decreasing background magnetic field strength lowers the energies of the peak(s) and causes the precipitation to increase at low energies and decrease at high energies at the start of the precipitation.

No MeSH data available.


Related in: MedlinePlus